Combination therapy including peripheral nerve field stimulation

ABSTRACT

Delivery of peripheral nerve field stimulation (PNFS) in combination with one or more other therapies is described. The other therapy delivered in combination with PNFS may be, for example, a different type of neurostimulation, such as spinal cord stimulation (SCS), or a drug. PNFS and the other therapy may be delivered simultaneously, in an alternating fashion, according to a schedule, and/or selectively, e.g., in response to a request received from a patient or clinician. A combination therapy that includes PNFS may be able to more completely address complex or multifocal pain than would be possible through delivery of either PNFS or other therapies alone. Further, the combination of PNFS with one or more other therapies may reduce the likelihood that neural accommodation will impair the perceived effectiveness PNFS or the other therapies.

This application is a continuation of U.S. application Ser. No.14/696,248, filed Apr. 24, 2015, now U.S. Pat. No. 9,320,847, which is acontinuation of U.S. application Ser. No. 14/109,049, filed Dec. 17,2013, now U.S. Pat. No. 9,020,599, which is a continuation of U.S.application Ser. No. 11/450,133, filed Jun. 9, 2006, now U.S. Pat. No.8,620,435, which claims the benefit of U.S. Provisional Application No.60/689,203, filed Jun. 9, 2005. U.S. application Ser. No. 11/450,133 isa continuation-in-part of each of U.S. application Ser. No. 11/374,852,filed on Mar. 14, 2006, now U.S. Pat. No. 7,813,803, Ser. No.11/375,492, filed on Mar. 14, 2006, now U.S. Pat. No. 7,890,166, andSer. No. 11/374,793, filed on Mar. 14, 2006, now U.S. Pat. No.8,244,360, each of which claims the benefit of U.S. ProvisionalApplication No. 60/700,627, filed on Jul. 19, 2005, and 60/761,823,filed on Jan. 25, 2006. The entire content of each of these applicationsis incorporated herein by reference.

TECHNICAL FIELD

The invention relates to medical devices, more particularly, to deliveryof therapies by medical devices to treat pain.

BACKGROUND

A variety of therapies, such as neurostimulation or therapeutic agents,e.g., drugs, may be delivered to a patient to treat chronic or episodicpain. Examples of neurostimulation therapies used to treat pain aretranscutaneous electrical nerve stimulation (TENS), percutaneouselectrical nerve stimulation (PENS), peripheral nerve stimulation (PNS),spinal cord stimulation (SCS), deep brain stimulation (DBS) and corticalstimulation (CS). Examples of drugs used to treat pain are opioids,cannabinoids, local anesthetics, baclofen, adenosine and alpha-blockers.

PNS, SCS, DBS and CS are typically delivered by an implantable medicaldevice (IMD). An IMD delivers neurostimulation therapy via electrodes,which are typically coupled to the IMD by one or more leads. The numberand positions of the leads and electrodes is largely dependent on thetype or cause of the pain, and the type of neurostimulation delivered totreat the pain. In general, an IMD delivers neurostimulation therapy inthe form of electrical pulses.

SCS involves stimulating the spinal cord at specifically targetedlocations, typically via leads and electrodes that are either surgicallyimplanted post laminectomy, or inserted percutaneously in the epiduralspace. Delivering stimulation to the appropriate location on the spinalcord causes paresthesia that overlay the pain region to reduce the areaof perceived pain. SCS can result in the patient experiencingparesthesia in a relatively large area, including more than one limb.

SCS has been shown to be effective for axial or longitudinal back pain,failed back surgery syndrome (FBBS), cervical pain, C1-C2 cervicogenicheadaches, supra-orbital pain, facial pain, inguinal and pelvic pain,and chest and intercostal pain. As examples, electrodes for SCS may beimplanted in the epidural space near vertebral levels T8-T10 to treataxial back pain, over the dorsal columns at vertebral levels T10-L1 totreat pain in the back, legs, ankles or feet, or over the dorsal roots,i.e., at the dorsal root entry zone, of vertebral levels L3-S1. SCS maybe most effective for neuropathic pain, such as neuropathy orradiculopathy that involves a significant portion of one limb and morethan one dermatome.

PNS is typically used to treat patients suffering from intractable painassociated with a single nerve. PNS places a group of electrodes in veryclose proximity to, e.g., in contact with, and approximately parallel toa major nerve in the subcutaneous tissue. PNS may also place a group ofelectrodes in very close proximity to a nerve that may be deeper in thelimb. Placing electrodes in very close proximity to the nerve may ensurethat only fibers within that nerve are activated at low amplitudes.

PNS electrodes may be located on percutaneous leads, but for stabilityand to prevent stimulation of other tissues proximate to the targetperipheral nerve, PNS electrodes are generally located within insulativematerial that wraps around a nerve, i.e. cuff electrodes, or on onesurface of a flat paddle of insulative material placed under a nerve. Inany case, the electrodes for PNS are placed in close proximity to thenerve “upstream” from the source of damage or pain, e.g., closer to thespinal cord than the region of damage or pain. When electrodes areimplanted upstream, the paresthesia resulting from PNS may extend to abroader area innervated by the target peripheral nerve. The most commonupper extremity nerves treated with PNS are the ulnar nerve, mediannerve, radial nerve, tibial nerve and common peroneal nerve.

DBS and CS can be used to treat neuropathic and nociceptive pain throughdelivery of stimulation to various structures of the brain. DBS maytreat pain through delivery of stimulation to gray matter within themidbrain, or the thalamus, via electrodes implanted in the brain. CS maytreat pain through delivery of stimulation to the sensory and/or motorcortex via electrodes placed in or on the cortex.

Therapeutic agents that treat pain may be delivered by an implantablepump, external pump, transdermally, or orally. Typically, an implantablepump delivers one or more therapeutic agents to a target location via acatheter. The target location may be intrathecal or extradural.

The pain experienced by a patient may be complex and/or multifocal.Complex or multifocal pain may include pain experienced by a patient atdifferent locations of the body, pain attributable to different causesor pathologies, and/or pain of different types, e.g., neuropathic and/ornociceptive pain. For some patients with complex and/or multifocal pain,any one of the pain treatment modalities identified above may be unableto completely treat the experienced pain. For example, SCS may notadequately treat pain in a large number of cases, perhaps the majority,because it has been shown to help neuropathic, but not nociceptive, painstates. Nociceptive pains can come from pressure, inflammation, andtemperature changes.

Further, over time, the nervous system of a patient may accommodate to aparticular treatment modality. Such neural accommodation may render apreviously effective modality, or dose or intensity for the modality,ineffective. Neural accommodation may result from noxious sensationsbeing rerouted to traverse alternative pathways in the nervous systemthat are not affected by the accommodated modality, at least at thecurrent dose or intensity. Simply increasing the dose or intensity of acurrent modality to overcome accommodation may not be effective, or maybe undesirable for a variety of reasons, such as increased battery orreservoir consumption, increased side-effects, or increased likelihoodof chemical dependency.

SUMMARY

In general, the invention is directed to techniques for deliveringperipheral nerve field stimulation (PNFS) in combination with one ormore other types of therapy, such as spinal cord stimulation (SCS). Acombination therapy that includes PNFS and one or more other types oftherapy may be able to more completely address complex and/or multifocalpain than would be possible through delivery of either PNFS or the othertherapies alone. Further, combining PNFS with one or more other types oftherapy may reduce the likelihood that neural accommodation will impairthe perceived effectiveness of any of the therapies.

PNFS is electrical stimulation delivered via one or more implantedelectrodes. The electrodes are positioned, i.e., implanted, in thetissue of a patient within the region where the patient experiencespain. The electrodes may be implanted within, for example, intra-dermal,deep dermal, or subcutaneous tissues of the patient. The PNFS currentmay spread along paths of lower resistance in any of numerous directionsfrom electrodes, but generally spreads parallel to the skin surface. ThePNFS current may spread over an area of several square centimeters. PNFSis not deliberately delivered to a specific nerve, but may excite nearlynerves.

Depending on the location at which the electrodes are implanted PNFS maybe used to treat a variety of types of pain. PNFS may be particularlyeffective at treating localized types of pain. For example, PNFS may beused to treat pain associated with failed back surgery syndrome (FBBS)or other low back pain, cervical pain, such as in the shoulder or neck,neuralgia or other pain associated with occipital nerves, supra-orbitalpain, facial pain, inguinal or other pelvic pain, intercostal or otherchest pain, limb pains, phantom limb pain, visceral pain, especially ifit is referred to a superficial structure, peroneal pain, or arthritis.

PNFS may ameliorate pain within the region through stimulation of axonsor small nerve fibers in the nearby dermal, subcutaneous, or musculartissues, or the tissues themselves. The stimulation of these axons orfibers may cause orthodromic action potentials that propagate toward thespinal cord, and modulate larger peripheral nerves and dorsal horn cellsand/or synapses within the dermatomes that include the pain region,which may reduce pain experienced by a patient in that region. Thepatient may experience paresthesia in the dermatome where the electrodesare placed. The stimulation of these axons or fibers may also causeantidromic action potentials that propagate toward the skin and modulatesympathetic outflow, which may reduce pain mediated by the sympatheticsystem, such as with some forms of complex regional pain syndrome. Theelectrodes that deliver PNFS are not deliberately implanted proximate toor aligned with larger, peripheral nerves, to avoid delivery ofstimulation to smaller fibers in the peripheral nerves, e.g., A-deltafibers, which may result in a patient experiencing unpleasantsensations.

By way of contrast, peripheral nerve stimulation (PNS), involvesdelivery of stimulation to a specific peripheral nerve via one or moreelectrodes implanted proximate to or in contact with a peripheral nerve,e.g., cuff electrodes surrounding the peripheral nerve. PNS may be usedto deliver stimulation to, for example, the vagal nerves, cranialnerves, trigeminal nerves, ulnar nerves, median nerves, radial nerves,tibial nerves, and the common peroneal nerves. When PNS is delivered totreat pain, one or more electrodes are implanted proximate to or incontact with a specific peripheral nerve that is responsible for thepain sensation.

PNS causes orthodromic action potentials to propagate to the spinal cordvia the specific peripheral nerve, diminishing pain. Typically, however,the electrodes are implanted proximate to the peripheral nerve,“upstream” from the region in which a patient perceives the pain, i.e.,closer to the spinal cord than the region of pain. For PNS therapy, itis considered desirable to implant the electrodes upstream from theregion in which a patient perceives pain so that the paresthesiaresulting from PNS is as widely distributed as the areas innervated bythe peripheral nerve, covering one or more complete dermatomes.

In some embodiments, the one or more implanted electrodes that deliverPNFS may be coupled to an implantable medical device (IMD) via one ormore implanted leads. In other embodiments, the IMD may include an arrayof one or more electrodes formed on a surface of the IMD housing, e.g.,as pad electrodes or ring electrodes, for delivery of PNFS. In suchembodiments, the IMD may include a miniaturized housing with a lowprofile that permits dermal or subcutaneous implantation in a region inwhich the patient experiences pain. In either case, the IMD generatesthe electrical stimulation for delivery via the electrodes. In someembodiments, the IMD includes pulse generation circuitry, and deliversPNFS in the form of electrical pulses.

In some embodiments, another type of neurostimulation therapy isdelivered in combination with PNFS. The PNFS and the otherneurostimulation may be delivered to respective sites via respectiveimplanted electrodes. The PNFS and other neurostimulation may bedelivered with different stimulation parameters, e.g., different pulseamplitudes, pulse widths, pulse rates, or electrode polarities. In someembodiments, a single IMD may deliver both the PNFS and the otherneurostimulation therapy to respective site via respective leads andsets of electrodes. In other embodiments, a plurality of IMDs maydeliver respective neurostimulation therapies. In such embodiments, oneor more of the IMBs may comprise a miniaturized housing with electrodesformed thereon for implantation and delivery of stimulation at aselected site, such as a region in which the patient experiences pain inthe case of PNFS.

As another example, the other therapy delivered in combination with PNFSmay be a drug, biological agent, genetic material, or other therapeuticagent. In such embodiments, the IMD may include a reservoir and pump todeliver the therapeutic agent. However, the other therapy delivered incombination with PNFS, whether electrical stimulation, a drug, or someother therapy, need not be delivered by the same IMD, as mentionedabove, or an IMD at all. For example, the other therapy may be deliveredby an external medical device, or a non-device delivery modality, suchas ingestion of a drug. SCS, PNS, deep brain stimulation (DBS), corticalstimulation, and one or more drugs are examples of other therapies thatmay be delivered in combination with PNFS.

PNFS and the one or more other therapies may be deliveredsimultaneously, or in an interleaved or alternating fashion. Forexample, when the combined therapies include a plurality ofneurostimulation therapies delivered by an IMD, the IMD may deliverpulses according to each of the therapies in an alternating orinterleaved fashion, e.g., each pulse delivered according to differentone of the therapies. As another example, the different neurostimulationtherapies may have different pulse rates, duty cycles or scheduled timesfor delivery, which may result in alternating delivery of the therapies.Interleaved or alternating delivery of PNFS and one or more othertherapies may, for example, reduce the likelihood that neuralaccommodation or tolerance to a particular drug will impair the efficacyof one or more of the therapies, while still providing therapy at anygiven time. Further, any or all of the combined therapies may bedelivered selectively, e.g., upon request by a user, such as a patientor physician.

In one embodiment, the invention is directed to a method for treatingpain of a patient that includes delivering peripheral nerve fieldstimulation to a region of a body of the patient in which a patientexperiences pain via at least one electrode implanted in the region, anddelivering at least one other therapy that treats pain to the patient incombination with the peripheral nerve field stimulation.

In another embodiment, the invention is directed to a system fortreating pain of a patient that includes at least one electrodeimplanted in a region of a body of the patient in which a patientexperiences pain, means for delivering peripheral nerve fieldstimulation via the at least one electrode, and means for delivering atleast one other therapy that treats pain to the patient.

In another embodiment, the invention is directed to a system fortreating pain of a patient that includes a first set of one or moreelectrodes implanted in a first region of a body of the patient in whichthe patient experiences pain, a second set of one or more electrodesimplanted in a second region of the body of the patient, and animplantable medical device coupled to the first and second sets ofelectrodes that delivers peripheral nerve field stimulation via thefirst set of electrodes and another neurostimulation therapy via thesecond set of a electrodes.

In another embodiment, the invention is directed to a system fortreating pain of a patient that includes a first implantable medicaldevice that delivers peripheral nerve field stimulation to a region of abody of the patient in which the patient experiences pain, and a secondmedical device that deliver sat least one other therapy that treats painto the patient.

The invention may provide advantages. For example, a combination therapythat includes PNFS and one or more other types of therapy may be able tomore completely address complex or multifocal pain than would bepossible through delivery of either PNFS or the other therapies alone.Pain areas involve a substantial portion of one limb, and involve morethan one dermatome. SCS is often used in this case. SCS may provideparesthesia to the lower back, an entire limb, and/or portions of morethan one limb. If a patient also has a focal site of pain (axial back,ribs, prior site of surgery, one knee), SCS may not ameliorate the pain,particularly if it is nociceptive pain. In such cases, PNFS may bedelivered to the site of the focal pain in combination with SCS or adifferent therapy to more completely address the pain experienced by thepatient. The PNFS might also allow strong activation of a part of apainful dermatome, even and SCS, PNS or other therapies give broader andless intense activation of that dermatome.

Further, the combination of PNFS with one or more other types of therapymay reduce the likelihood that neural accommodation will impair theperceived effectiveness of any of the therapies. Constant delivery of atherapy may lead to neural accommodation. PNFS and another therapy maybe delivered at alternate times to avoid constant delivery of eithertherapy while providing substantially consistent relief of the painexperienced by a patient. Additionally, delivering PNSF with anothertherapy may allow pain to be ameliorated while avoiding problemsassociated with increased intensities or doses of therapies, such asincreased battery or reservoir consumption, increased side-effects, orincreased likelihood of chemical dependency. Also, systems according tothe invention may advantageously allow patients to selectively choosedelivery of one or more therapies from among a plurality of therapymodalities, including PNFS, to address their needs.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram illustrating an example system fordelivering peripheral nerve field stimulation (PNFS) and one or moreother types of therapy to a patient in accordance with an embodiment ofthe invention.

FIG. 2 is a conceptual diagram illustrating another example system fordelivering PNFS and one or more other types of therapy to a patient.

FIG. 3 is a conceptual diagram illustrating another example system fordelivering PNFS and one or more other types of therapy to a patient.

FIG. 4 is a block diagram illustrating an example implantable medicaldevice for delivering PNFS and one or more other types of therapy to apatient.

FIG. 5 is a block diagram illustrating an example clinician programmerthat allows a clinician to program PNFS and one or more other types oftherapy for a patient.

FIG. 6 is a block diagram illustrating an example patient programmerthat allows a patient to control delivery of PNFS and one or more othertypes of therapy by an implantable medical device.

FIGS. 7A-7F are timing diagrams illustrating delivery of PNSF incombination with another neurostimulation therapy according toembodiments of the invention.

FIGS. 8A-8C are schematic diagrams illustrating a top and side views ofexample implantable medical leads having a plurality of electrodeslocated on more than one surface of the lead.

FIGS. 9A-9E are schematic diagrams illustrating top views of otherexample implantable medical leads having a plurality of electrodeslocated on more than one surface of the lead.

FIGS. 10A-10D are schematic diagrams illustrating side views of otherexample implantable medical leads with electrodes positioned on varioussurfaces.

FIG. 11 is a schematic diagram illustrating an example implantablemedical lead including fixation structures.

FIG. 12 is a conceptual diagram illustrating another example system fordelivering peripheral nerve field stimulation (PNFS) and one or moreother types of therapy to a patient, the system including multipleimplantable medical devices.

FIGS. 13A and 13B are schematic diagrams respectively illustrating topand side views of the implantable medical device of FIG. 1 withelectrodes located on a top surface and a bottom surface of theimplantable medical device housing.

FIGS. 14A and 14B are schematic diagrams respectively illustrating topand side cross-sectional views of the implantable medical device of FIG.13.

FIGS. 15A and 15B are schematic diagrams respectively illustrating topand side cross-sectional views of another example implantable medicaldevice with electrodes located on multiple housing surfaces, in whichthe housing includes a bend.

FIG. 16 is a schematic diagram illustrating a side cross-section view ofanother example implantable medical device with electrodes located onmultiple housing surfaces and in which the housing includes a bend.

FIG. 17 is a schematic diagram illustrating a side cross-section view ofanother example implantable medical device with electrodes located onmultiple housing surfaces, in which the housing includes a bellows thatallows the housing to conform to an implant site.

FIG. 18 is a schematic diagram illustrating a side view of an exampleimplantable medical device with ring electrodes located along a bentcylindrical housing.

FIGS. 19 and 20 are schematic diagrams illustrating side views of acylindrical implantable medical device that is flexible at a bellowsjoint.

FIGS. 21A and 21B are schematic diagrams respectively illustrating abottom view and a side cross-sectional view of another exampleimplantable medical device with electrodes located on multiple housingsurfaces, in which the top and bottom housing surfaces are respectivelyconvex and concave.

FIG. 22 is a schematic diagram illustrating a bottom view of anotherexample implantable medical device with electrodes located on multiplehousing surfaces, in which the housing includes relatively rigid andrelatively flexible portions.

FIG. 23 is schematic diagram illustrating a side cross-sectional view ofanother example implantable medical device with electrodes located onmultiple housing surfaces, in which the electrodes are recessed into thehousing surfaces.

FIG. 24 is schematic diagram illustrating another example implantablemedical device coupled to an additional array of electrodes.

FIG. 25 is a flow diagram illustrating an example method ofmanufacturing an implantable medical device with electrodes located onmultiple housing surfaces.

FIG. 26 is a block diagram illustrating an example control module for animplantable medical device.

DETAILED DESCRIPTION

FIG. 1 is a conceptual diagram illustrating an example system 10 fortreating pain of a patient 12 by delivering peripheral nerve fieldstimulation (PNFS) in combination with one or more other types oftherapy that treat pain to the patient. Through delivery of acombination therapy that includes PNFS and one or more other types oftherapy, system 10 may be able to more completely address complex ormultifocal pain than would be possible through delivery of either PNFSor the other therapies alone. In addition, the combination of PNFS withone or more other types of therapy may reduce the likelihood that neuralaccommodation or plasticity will impair the perceived effectiveness ofany of the therapies.

System 10 includes an implantable medical device (IMD) 14 that deliversPNFS therapy and at least one other type of therapy to patient 12.However, the invention is not limited to embodiments in which a singleIMD 14 delivers more than type of therapy, such as is illustrated inFIG. 1. In some embodiments, a separate IMD or external medical devicemay deliver a therapy in combination with the PNFS delivered by IMD 14.In some embodiments in which multiple medical devices deliver differenttherapies, the devices may communicate to coordinate delivery of thetherapies, e.g., wirelessly via radio frequency or body conduction.

As mentioned above, IMD 14 may deliver another neurostimulation therapyin combination with PNFS. In the illustrated embodiment, IMD 14 deliversspinal cord stimulation (SCS) to the spinal cord 18 of patient 12 incombination with delivery of PNFS. In other embodiments, an IMD maydeliver one or more of peripheral nerve stimulation (PNS), deep brainstimulation (DBS) and cortical stimulation (CS) in combination withPNFS. SCS, PNS, DBS and CS are examples of other neurostimulationtherapies that may be delivered in combination with PNFS. The inventionis not limited to delivery of the identified neurostimulation therapies,or any neurostimulation thearapy, in combination within PNFS. Anystimulation therapy may be delivered in combination with PNFS.

Further, the invention is not limited to embodiments in which the othertherapy that treats pain is a type of stimulation. In some embodiments,for example, a drug or other therapeutic agent may be delivered incombination with PNFS. A single IMD may include circuitry to deliverPNFS, and a reservoir and pump to deliver the drug. Alternatively,systems that deliver a drug in combination with PNFS may include aseparate implantable or external pump, or a transdermal deliverymechanism, such as a patch. In some embodiments, a drug is taken orallyby a patient in combination with delivery of PNFS.

IMD 14 may include circuitry for the generation of electrical pulses,and deliver PNFS and other types of neurostimulation in the form ofelectrical pulses. IMD 14 delivers PNFS via a first set of one or moreelectrodes (not shown in FIG. 1) carried by a lead 16, and SCS via asecond set of electrodes (not shown in FIG. 1) carried by lead 17.

Lead 16 may deliver PNFS to the tissue of patient 12 within a region 19where patient 12 experiences pain. Lead 16 may be implanted within orbetween, for example, intra-dermal, deep dermal, or subcutaneous tissuesof patient 12 at the region 19 where patient 12 experiences pain todeliver PNFS. These tissues include skin and associated nerves andmuscles and associated nerves or muscle fibers. In the illustratedexample, region 19 is an axial region of the lower back of patient 12,but the invention is not limited as such. Rather, lead 16 may beimplanted in any region where patient 12 experiences pain. Lead 16 maydeliver PNFS to one layer of tissue or multiple layers of a tissue asdetermined necessary by a physician.

For example, in other embodiments, lead 16 may extend from IMD 14 to anylocalized area or dermatome in which patient 12 experiences pain. Forexample, lead 16 may extend from IMD 14 to position electrodes atvarious regions of the back, the back of the head, above the eyebrow,and either over the eye or under the eye, and may be used to treatfailed back surgery syndrome (FBBS), cervical pain (shoulder and neckpain), facial pain, headaches supra-orbital pain, inguinal and pelvicpain, chest and intercostal pain, mixed pain (nociceptive andneuropathic), visceral pain, neuralgia, peroneal pain, phantom limbpain, and arthritis. PNFS may ameliorate pain within the region ofimplantation by stimulating axons or small nerve fibers in the nearbydermal, subcutaneous, or muscular tissues, or the tissues themselves.The stimulation of these axons or fibers may cause orthodromic actionpotentials that propagate toward spinal cord 18, and modulate largerperipheral nerves and dorsal horn cells and/or synapses within thedermatomes that include the pain region, which may reduce painexperienced by 12 patient in that region. The stimulation of these axonsor fibers may also cause antidromic action potentials that propagatetoward the skin and modulate sympathetic outflow, which may reduce painmediated by the sympathetic system, such as with some forms of complexregional pain syndrome. Lead 16 is not implanted proximate to larger,peripheral nerves in order to avoid delivery of stimulation to smallerfibers in the nerve, e.g., A-delta fibers, which may result in a patientexperiencing unpleasant sensations.

Lead 16 may comprise, as examples, a substantially cylindrical lead withring electrodes, a paddle lead, or a lead within a more complex,three-dimensional electrode array geometry, such as a cylindrical leadwith electrodes disposed at various circumferential positions around thecylinder. In some embodiments, as discussed in greater detail below, thelead may have electrodes, such as pad electrodes on more than onesurface. For example, lead 16 may be a paddle-type lead with electrodeson multiple surfaces, or a multiple level lead, as will be described ingreater detail below. The invention is not limited to use of any of theleads described herein, or any particular type of implantable lead.

IMD 14 may deliver another type of neurostimulation to patient 12 vialead 17 to treat pain in combination with the PNFS delivered via lead16. In the illustrated embodiment, lead 17 extend to spinal cord 18, andIMD 14 delivers SCS via the one or more electrodes carried by lead 17.The electrodes may be implanted in, for example, an epidural space orproximal to the dorsal root entry zone of patient 12. In someembodiments, the electrodes are located within a region defined byvertebral levels T7-L1. For example, lead 17 may be implanted in theepidural space near vertebral levels T8-T10 to treat axial back pain,over the dorsal roots of L3-S1, over the dorsal columns at vertebrallevels T10-L1 to treat pain in the ankle or foot, or near vertebrallevels T9-T11 give paresthesia to the entire thigh. SCS may be mosteffective at treating neuropathic pain, such as neuropathy orradiculopathy that involves a substantial portion of one limb and morethan one dermatome.

However, the invention is not limited to embodiments in which lead 17extends to spinal cord 18, or IMD 14 delivers SCS. In other embodiments,for example, lead 17 may extend to a location closely proximate to aparticular peripheral nerve responsible for causing patient 12 toexperience pain, and IMD 14 may deliver PNS to the peripheral nerve. Thelocation that the patient experiences pain may be the location that thepatient perceives the pain to be. In still other embodiments, lead 17may extend to the brain of patient 12 (not shown) via a hole formed inthe cranium of the patient, and IMD 14 may deliver DBS or CS. For DBS,electrodes may be implanted within the brain, and for CS, electrodes maybe implanted within or proximate to the brain.

The number and position of leads 16, 17 illustrated in FIG. 1 isexemplary. Multiple leads 16, 17 may extend to each location thatreceives stimulation from IMD 14. For example, four leads 16, each withtwo electrodes, may extend to a particular region 19 where patient 12experiences pain, and two leads 17, each with eight electrodes mayextend to spinal cord 18. Leads 16, 17 may be bifurcated, particularlyif the number of interfaces that IMD 14 provides for leads 16, 17 islimited. Although not shown in FIG. 1, leads 16, 17 may be coupled toIMD 14 by one or more extensions. In some embodiments, IMD 14 may alsoinclude additional leads so as to deliver more than one other therapy incombination with PNFS.

As described herein, leads 16 and 17 may be positioned to deliver PNFSin combination with other types of therapy in order to address complexor multifocal pain. Many cases of axial pain are complex, i.e., bothneuropathic (prior nerve injury) and nociceptive (ongoing stimuli).Additionally, a patient may have pain localized in a small area that isuniformly unresponsive to SCS or PNS. For example, a patient mayexperience arthritis pain in part of one limb, trunkal pain ofpost-herpetic neuralgia (PHN), or limb pain from advanced complexregional pain syndrome (CRPS) after trophic changes are irreversible.Current advanced pain management therapies for neuropathic pain,nociceptive pain, and/or axial pain may have effective treatment for aportion of the pain experienced by patient 12, but do not always relievea patient from their pain entirely. For example, when delivering onlySCS, the patient may still experience nociceptive pain since SCS onlytreats neuropathic pain.

As an example, patients with failed back surgery syndrome (FBBS) oftenhave both axial pain due to pressure, instability, inflammation andnerve damage near the vertebra, and radiculopathy down one or both legsdue to prior damage to nerve roots. Typically, only one modality oftherapy, such as stimulation or drugs, is used since each modality hasan implanted device that has its own advantages and disadvantages.Consequently, a physician may pick the modality that treats the worstpain even though pain location, nature, intensity, and other paincharacteristics may change over time.

For example, SCS delivered via a set of electrodes at vertebral levelsT8-T10 may be used to treat axial pain and, in some cases, may even giveparesthesia into parts or all of the legs. However, such SCS stimulationoften cannot give paresthesia into the feet, since fibers ascending inthe dorsal columns from feet are small and possibly deep at themid-thoracic levels. Thus, another set of electrodes may be implantedover the dorsal roots at L3-S1, or over the vertebral levels T10-L1.However, the relief of axial pain may fade over a period of time becauseeven with delivering stimulation to different areas of the spinal cordthe patient may focus on the remaining axial pain and may be relativelydissatisfied.

Furthermore, even if a patient has only axial back pain, or pain in alocalized region of the trunk, using only one modality of stimulationmay not be sufficient to relieve a substantial amount of the painexperienced by the patient. Moreover, SCS alone has a limitation forpain in the upper arms and neck since leads placed in the epidural spaceat the upper thoracic and cervical vertebral levels often movesignificantly relative to the spinal cord. Consequently, the level ofparesthesia can change dramatically thereby preventing sleep or useduring normal movements.

In addition, the nervous system has many parallel paths that communicatesensations, including pain, to the brain. Examples of such paths includethe lateral spinothalamic paths, the dorsal columns (especially forvisceral pain), the spinoreticular paths (for alerting), andspinocerebellar paths. When one of the paths is interrupted to diminishpain, the pain often eventually returns via another pathway.

PNFS can be used in combination with other therapies to affect differentbrain and spinal areas separately. In particular, delivering PNFS incombination with one or more other therapies may provide a synergisticeffect by targeting different portions of the neural “circuit” therebyreducing the likelihood that neural accommodation will reduce theefficacy of one of the therapies. Thus, delivering PNFS in combinationwith one or more other therapies may more completely address complexpain than would be possible through delivery of either PNFS or the othertherapies alone.

IMD 14 may deliver PNFS in combination with other types of therapysimultaneously, or in an interleaved or alternating fashion. Forexample, when the combined therapies include a plurality ofneurostimulation stimulation therapies, IMD 14 may deliver electricalpulses according to each of the therapies in an alternating orinterleaved fashion, e.g., each pulse delivered according to a differentone of the therapies. Consequently, the delivery of each therapy can beoptimized at each site.

As another example, the different electrical stimulation therapies mayhave different pulse rates, duty cycles, or scheduled times fordelivery, which may result in alternating delivery of therapies. Thus,electrical pulses can be interleaved so as to deliver the same frequencyof electrical pulses to respective sites, but with varying amplitudes orpulse widths. Alternatively, a packet of pulses may be delivered to aPNFS site, with or without ramping of amplitude from start to finish,followed by delivering another packet of pulses to, for example, a SCSsite.

Interleaved or alternating delivery of PNFS and one or more otherelectrical stimulation therapies may, for example, reduce the likelihoodthat neural accommodation or plasticity will impair the efficacy of oneor more of the therapies, while still providing therapy at any giventime. In particular, avoiding constant stimulation at a site, PNFS orotherwise, may prevent neural accommodation that would reduce theefficacy of one or more of the therapies. Interleaved or alternatingdeliver of PNFS and one or more other electrical stimulation therapiesmay also prevent overuse or depletion of transmitters, such as GABA-B,that are major inhibitory transmitters released in the dorsal horn whenelectrical stimulation produces pain relief. Further any or all of thecombined therapies may be delivered selectively, e.g. upon request by auser, such as a physician or a patient. In other words, system 10 mayprovide multiple therapies that may be selected by a user, e.g., as thepain experienced dictates, but need not deliver a plurality of therapiesat all times.

System 10 also includes a clinician programmer 20. Clinician programmer20 may, as shown in FIG. 1, be a handheld computing device. Clinicianprogrammer 20 includes a display 22, such as a LCD or LED display, todisplay information relating to PNFS and one or more of the othertherapies to a user. Clinician programmer 20 may also include a keypad24, which may be used by a user to interact with clinician programmer20. In some embodiments, display 22 may be a touch screen display, and auser may interact with clinician programmer 20 via display 22. A usermay also interact with clinician programmer 20 using peripheral pointingdevices, such as a stylus or mouse. Keypad 24 may take the form of analphanumeric keypad or a reduced set of keys associated with particularfunctions.

A clinician or physician (not shown) may use clinician programmer 20 toprogram PNFS and the at least one other therapy for patient 12. Inparticular, the clinician may use clinician programmer 20 to selectvalues for therapy parameters, such as pulse amplitude, pulse width,pulse rate, electrode polarity and duty cycle, for both the PNFS and theother therapy. Infusion rate, concentration, ratio (if two or more drugsare delivered), and duty cycle are examples of therapy parameters fordrug delivery. IMD 14 may deliver the PNFS and the other therapyaccording to respective programs, each program including respectivevalues for each of a plurality of such therapy parameters. In someembodiments, varying the pulse frequency may allow PNFS to capturetarget nerve fibers, such as small, medium, or large fibers sensitive topulse frequency.

Further, IMD 14 may deliver PNFS in combination with other therapy inaccordance with a program group. A program group may contain one or moreprograms. A program group may include one or more PNFS programs and oneor more programs for the other therapy. IMD 14 may deliver stimulationpulses according to a program group by “interleaving” the pulses foreach program, e.g., delivering each successive pulse according to adifferent one of the programs of the program group. To create a programsand program groups the clinician may select existing or predefinedprograms, or specify programs by selecting therapy parameter values. Theclinician may test the selected or specified programs on patient 12, andreceive feedback from patient 12. Highly rated programs may be providedto IMD 14 or a patient programmer, individually or as program groups,and used by IMD 14 to control delivery of stimulation. The clinician mayidentify preferred programs for PNFS and one or more other therapiesseparately or through delivery of the therapies together.

System 10 also includes a patient programmer 26, which also may, asshown in FIG. 1, be a handheld computing device. Patient programmer 26may also include a display 28 and a keypad 30, to allow patient 12 tointeract with patient programmer 26. In some embodiments, display 28 maybe a touch screen display, and patient 12 may interact with patientprogrammer 26 via display 28. Patient 12 may also interact with patientprogrammer 26 using peripheral pointing devices, such as a stylus ormouse.

Patient 12 may use patient programmer 26 to control the delivery of PNFSand the at least one other therapy by IMD 14. Patient 12 may use patientprogrammer 26 to activate or deactivate PNFS, the one or more othertherapies, or both, and may use patient programmer 26 to select theprograms or program group that will be used by IMD 14 to deliver PNFS incombination with one or more other types of therapy. Further, patient 12may use patient programmer 26 to make adjustments to programs or programgroups. Additionally, the clinician or patient 12 may use programmers20, 26 to create or adjust schedules for delivery of PNFS, the one ormore other therapies, or both. Such schedules may provide foralternating delivery of PNFS and the one or more other therapies.

IMD 14, clinician programmer 20 and patient programmer 26 may, as shownin FIG. 1, communicate via wireless communication. Clinician programmer20 and patient programmer 26 may, for example, communicate via wirelesscommunication with IMD 14 using any telemetry techniques known in theart. Such techniques may include low frequency or radiofrequency (RF)telemetry, but other techniques are also contemplated. Clinicianprogrammer 20 and patient programmer 26 may communicate with each otherusing any of a variety of local wireless communication techniques, suchas RF communication according to the 802.11 or Bluetooth specificationsets, infrared communication according to the IRDA specification set, orother standard or proprietary telemetry protocols. Clinician programmer20 and patient programmer 26 need not communicate wirelessly, however.For example, programmers 20 and 26 may communicate via a wiredconnection, such as via a serial communication cable, or via exchange ofremovable media, such as magnetic or optical disks, or memory cards orsticks. Further, clinician programmer 20 may communicate with one orboth of IMD 14 and patient programmer 26 via remote telemetry techniquesknown in the art, communicating via a local area network (LAN), widearea network (WAN), public switched telephone network (PSTN), orcellular telephone network, for example.

FIG. 2 is a conceptual diagram illustrating another example system fordelivering PNFS and one or more other types of therapy to a patient. Asshown in FIG. 2, system 30 is similar to system 10; however, system 30is utilized at a different location in patient 32. System 30 of FIG. 2delivers PNFS in combination with SCS via IMD 38 and coupled leads 42and 40. However, unlike system 10, system 20 delivers PNFS via lead 42to a region 36 on the face of a patient 32 where the patient experiencespain, and SCS via lead 40 to a region at the level of the C1-C3vertebrae of patient 32. The PNFS may, for example, alleviatesupra-orbital or suborbital facial pain, while the SCS providesparesthesia to the back of the head and neck to alleviate, for example,headaches or migraines. In this manner, system 30 may more completelyaddress a complex pain which would not be possible through delivery ofPNFS of SCS alone.

System 30 includes an IMD 38 coupled to leads 42 and 40 that includeelectrodes, which may be substantially similar to and performsubstantially similar functions as IMD 14 and leads 16 and 17 depictedand described above with reference to FIG. 1. System 30 may also includeclinician and patient programmers 44 and 46, respectively, which may besubstantially similar to and perform substantially similar functions asprogrammers 20, 26 depicted and described above with reference toFIG. 1. IMD 38 may deliver PNFS and SCS according to programs selectedwith one of programmers 44 or 46 and stored within a memory of IMD 38.Each stimulation program may include different therapy parameter values,and IMD 38 may deliver stimulation according to the programs in asimultaneous, interleaved, or alternating fashion, in any of the mannersdescribed above.

FIG. 3 is a conceptual diagram illustrating another example system fordelivering PNFS and one or more other types of therapy to a patient. Asshown in FIG. 3, system 48 delivers PNFS to a region 52 where a patient50 experiences pain, in combination with SCS and drug therapies. System48 includes an IMD 54 that delivers PNFS and SCS via electrodes locatedon leads 58 and 56, respectively. Alternatively, separate IMDs maydeliver PNFS and SCS. In such embodiments, the IMDs may communicate tocoordinate therapy, e.g., wirelessly via radio frequency or electricalconduction through the body of patient 32. In the illustratedembodiment, drug therapy is also delivered to patient 50 at site 52where pain is experienced by a patch 60 through which patient 50transdermally absorbs a drug. Patch 60 is an example of an externalmedical device that delivers a therapy to patient 50.

For example, IMD 54 may deliver PNFS in combination with SCS and drugtherapy in the manner illustrated by FIG. 3 for treatment of failed backsurgery syndrome (FBBS) in which patient 50 experiences both axial painand radiculopathy down one or both legs. In particular, IMD 54 maydeliver PNFS at site 52 to treat axial back pain and SCS to the dorsalcolumns or dorsal roots of the spinal cord to treat radicular pain.Patient 50 may absorb drugs through patch 60 at site 52 to furtherrelieve pain experienced at the site or enhance the PNFS therapy.Consequently, system 48 may more completely address complex pain thanwould be possible through delivery of PNFS, SCS, or drug therapy alone.

Lead 58 may be implanted in intra-dermal, deep dermal, or subcutaneoustissues of patient. In the illustrated embodiment, lead 58 extends fromIMD 54 to the lower back of patient 50 to relieve pain, e.g. axial backpain, in region 52. Lead 56 may extend from IMD 54 over the dorsal rootsat vertebral levels L3-S1 or over dorsal columns at vertebral levelsT10-L1 to relieve radicular pain in one or both legs. IMD 54 may deliverPNFS and SCS simultaneously, or in interleaved or alternating fashion.Interleaved or alternating delivery of PNFS and SCS may reduce thelikelihood that neural accommodation will impair the efficacy of thetherapies while still providing one of the therapies at any given time.

In addition, patch 60 delivers drug therapy to patient 50 at region 52.Patch 60 absorbs a drug through the patch. However, the invention is notlimited as such. In some embodiments drug therapy may be deliveredorally, intrathecally, or extradurally. In additional embodiments, IMD54 may also include a reservoir and drug pump to deliver the drug toregion 52 or another location via a catheter. Examples of drugs that beused are opioids, cannabinoids, anti-inflammatory agents, steroids,baclofen, adenosine, local anesthesia, anti-depressants, and alphaagonists. Delivered drugs may, for example, diminish pain by their ownaction, especially when applied to specific sites, enhance the benefitsof electrical stimulation, and treat particular pain modalities.Nociceptive pain may be treated through delivery of morphine, forexample, and the action of specific nerves may be blocked throughdelivery of local anesthetics. Consequently, delivering PNFS incombination with drug therapy may more completely address complex painthan would be possible through the delivery of one of the othertherapies alone. As one example of the synergy between therapies, PNFSdelivered to region 52 by IMD 54 may reduce allodynia, thereby allowingpatch 60 to be applied to the skin of patient 50 to deliver drugtherapy.

System 48 includes an IMD 54 coupled to leads 58 and 56 that includeelectrodes, which are substantially similar to and perform substantiallysimilar functions as IMD 14 and leads 16 and 17 depicted and describedabove with reference to FIG. 1. System 48 may also include clinician andpatient programmers 62 and 64, respectively, which may be substantiallysimilar to and perform substantially similar functions as programmers20, 26 depicted and described above with reference to FIG. 1. IMD 54 maydeliver PNFS and SCS according to respective programs or program groupsstored within a memory of the IMD, according to different therapyparameter values, and in a simultaneous, interleaved, or alternatingfashion, in any of the manners described above.

Other therapy combinations may be provided by the systems describedherein. Table 1 below illustrates various combinations of PNFS therapywith other types of therapy to relieve pain associated with a number ofconditions. In particular, each row of the table provides an“indication” that is treated, a location or “site” at which to deliverPNFS, reason(s) for delivering PNFS at the site, various sites at whichto deliver other therapies and the reasons for delivering the othertherapy types. The other types of therapy delivered in combination withPNFS include SCS, PNS, and various forms of DBS and CS. As used in Table1, the acronyms PVG and PAG refer to midbrain gray matter stimulationlocations, and the acronyms VPL and VPM refer to thalamic stimulationlocation. More particularly, PVG, PAG, VPL and VPM respectively refer toa periventricular gray, periaqueductal gray, ventroposterior lateralnucleus and ventroposterior medial nucleus stimulation locations.

For example, PNFS may be delivered in combination with SCS, PNS, DBSand/or CS to treat axial back pain. In this case, approximately one tofour leads having approximately four to sixty-four electrodes may beimplanted in the intra-dermal, deep-dermal, or subcutaneous tissue atregion where the patient experiences pain. SCS may be delivered to theT7-T10 vertebral levels in combination with PNFS to give paresthesiainto the back. PNS may be delivered to a branch of the median nerve incombination with PNFS to treat facet pain that the patient mayexperience in addition to the axial back pain. DBS may be delivered toPVG, PAG, or VPL locations in combination with PNFS to treat neuropathiccomponents of the pain. CS may also be delivered to the motor cortex,near the midline in combination with PNFS to treat neuropathiccomponents.

As another example, PNFS may be delivered in combination with SCS, DBSand/or CS to treat occipital neuralgia and headaches. In this case,electrode groups for PNFS may be implanted in a line transverse to theC2 and C3 nerve branches. Fascia, muscle, or tendons may be between thegroups of electrodes and the nerves in order reduce the likelihood ofunpleasant stimulation. SCS may be delivered to the C1-C3 nerves incombination with PNFS to give paresthesia into the back. DBS may bedelivered to PVG, PAG, or VPM locations in combination with PNFS totreat neuropathic components of the pain, or triggers of the migraines.CS may be delivered to the lateral part of the motor cortex incombination with PNFS to also treat neuropathic components or triggers.

In another example, PNFS may be delivered in combination with PNS, DBSand/or CS to treat temporomandibular join pain. In this case, electrodesfor PNFS may be implanted in front of the ear to deliver stimulation toor near the region where the patient experiences pain. PNS may bedelivered to branches of the trigeminal nerve (V), including deliveringPNS in the Gasserian ganglia foramen, in combination with PNFS torelieve neuropathic pain. DBS may be delivered to PVG, PAG, or VPMlocations in combination with PNFS to give paresthesia into the face ofthe patient. CS may be delivered to the lateral part of the motor cortexin combination with PNFS to treat neuropathic components of the pain.

A common patient problem for stimulation therapies today is acombination of axial back pain and radiculopathy, which is often a formof failed back surgery syndrome (FBBS). In a further example, PNFS maybe delivered in combination with SCS, PNS, DBS and/or CS to treat FBBS.SCS can work very well for the radiculopathy, especially for the lowerlimbs, but its success for the axial pain can be less, especially aftersix or more months. In this case, PNFS in the painful areas of the backcan help the axial pain, and the SCS part of the combined system candeal well with the radicular symptoms.

The following combination of therapies may provide relief from axialpain and radiculopathy associated with FBBS. In this case, approximatelyone to four electrode leads having approximately four to sixty-fourelectrodes may be implanted in intra-dermal, deep-dermal, orsubcutaneous tissue in a region where the patient experiences pain fordelivery of PNFS. SCS may be delivered to the T7-T10 vertebral levels aswell as the T10-L1 vertebral levels in combination with PNFS to giveparesthesia into the back, leg, and/or foot. DBS may be delivered toPVG, PAG, or VPL locations in combination with PNFS to treat neuropathiccomponents of the pain. CS may be delivered near the midline of themotor cortex in combination with PNFS to treat neuropathic components ortriggers.

In yet another example, PNFS may be delivered in combination with SCS,DBS and/or CS to treat supra-orbital or sub-orbital facial pain. In thiscase, electrode groups for PNFS may be implanted in a line above orbelow the eye, e.g., roughly parallel to the eyebrow, to deliverstimulation to branches of the facial nerve (VIII). In this case, SCSmay be delivered to the C1-C3 nerves in combination with PNFS to giveparesthesia into the back of the head and neck. DBS may be delivered toPVG, PAG, or VPM locations in combination with PNFS to treat neuropathiccomponents or triggers. CS may be delivered to the lateral part of themotor cortex in combination with PNFS to treat neuropathic components ortriggers.

In a further example, PNFS may be delivered in combination with SCS,PNS, DBS and/or CS to treat arthritis. In this case, electrode groupsmay be implanted in intra-dermal, deep-dermal, or subcutaneous tissue inany region where the patient experiences arthritis pain. SCS may bedelivered to the C4-C8 vertebral levels for upper limb pain and to theT10-L1 vertebral levels for hip, knee, ankle and foot pain incombination with PNFS to give paresthesia into the painful area. PNS maybe delivered to an appropriate major arm or leg nerve in combinationwith PNFS to give paresthesia into the painful area. DBS may bedelivered to PVG, PAG, or VPL locations in combination with PNFS totreat neuropathic components or triggers. CS may be delivered near themidline of the motor cortex in combination with PNFS to treatneuropathic components in the leg and feet. CS may also be deliverednear the lateral part of the motor cortex in combination with PNFS totreat neuropathic components in the arm and hand.

In another example, PNFS may be delivered in combination with SCS, PNS,DBS and/or CS to treat inguinal pain. In this case, electrode groups maybe implanted in intra-dermal, deep-dermal, or subcutaneous tissue in anyregion where the patient experiences pain to give nonpainful PNFSstimulation to the painful area. SCS may be delivered to the T4-L1vertebral levels in combination with PNFS to give paresthesia into thepainful area. PNS may be delivered via electrodes implanted deeper alongthe nerves involved in the pain in combination with PNFS to giveparesthesia into the painful area. DBS may be delivered to PVG, PAG, orVPL locations in combination with PNFS to treat neuropathic componentsor triggers. CS may be delivered near the midline of the motor cortex incombination with PNFS to treat neuropathic components in the leg andfeet.

In another example, PNFS may be delivered in combination with SCS, PNS,DBS and/or CS to treat arthritis. In this case, electrode groups may beimplanted in intra-dermal, deep-dermal, or subcutaneous tissue in anyregion where the patient experiences pain to give nonpainful PNFSstimulation to the painful area. SCS may be delivered to the T8-L1vertebral levels in combination with PNFS to give paresthesia into thepainful area. PNS may be delivered to the pudendal nerve in combinationwith PNFS to treat neuropathic components. DBS may be delivered to PVG,PAG, or VPL locations in combination with PNFS to treat neuropathiccomponents or triggers. CS may be delivered near the midline of themotor cortex in combination with PNFS to treat neuropathic components inthe lower body.

In another example, PNFS may be delivered in combination with SCS, PNS,DBS and/or CS to treat angina, or pain associated with other heartdysfunction, such as arrhythmia. In this case, electrodes may beimplanted over the heart, any part of the thorax or at any region wherethe patient experiences pain, such as in the arms, jaw, or back. Forexample, electrodes may be implanted within or between intra-dermal,deep dermal, or subcutaneous tissues of the chest. Delivering PNFS inthis manner may reduce angina attacks. A two-sided paddle for PNFS wouldbe especially useful to deliver different parameters of stimulation tothe cutaneous areas and their nerves versus the underlying muscle andits nerves. SCS may be delivered to the C1-T4 vertebral levels incombination with PNFS to give paresthesia into the painful area andreduce angina. PNS may be delivered to the vagus nerve in combinationwith PNFS to slow the heart and, thus, reduce stress on the heart. PNSmight also be delivered to any of the major nerves in the arm,especially those which may have referred pain from cardiac noiception.DBS may be delivered to PVG, PAG, or VPL locations in combination withPNFS to treat neuropathic components. DBS may also be delivered tonuclei near the hypothalamus or in the ventral lateral medulla incombination with PNFS to lower blood pressure, which may reduce pain byreducing the stress on the heart. CS may be delivered severalcentimeters off the midline of the motor cortex in combination with PNFSto treat neuropathic components.

In yet another example, PNFS may be delivered in combination with SCS,PNS, DBS and/or CS to treat cancer pain or phantom limb pain. In thiscase, electrode groups may be implanted in intra-dermal, deep-dermal, orsubcutaneous tissue in a region where the patient experiences pain togive non-painful stimulation to the painful region. SCS may be deliveredat a level appropriate to the pain experienced by the patient incombination with PNFS to give paresthesia into the painful area. PNS maybe delivered to a nerve involved in the pain in combination with PNFS totreat neuropathic components of the pain. DBS may be delivered to PVG,PAG, VPL, or VPM locations in combination with PNFS to treat neuropathiccomponents or triggers. CS may be delivered at an appropriate locationof the motor cortex in combination with PNFS to treat neuropathiccomponents of the pain.

TABLE 1 Reason for Reason for Site for Delivering Site for DeliveringIndication PNFS PNFS other Therapy Other Therapy Axial back pain Axialback, 1-4 Deliver SCS: T7-T10 Gives leads, 4-64 stimulation toparesthesia into electrodes the region where the back patient PNS:branch Also treat facet experiences pain of median pain nerve DBS: PVGor Treat PAG nociceptive components DBS: VPL Treat neuropathiccomponents CS: motor Treat cortex, near neuropathic midline componentsOccipital Electrode Deliver SCS: C1-C3 Gives neuralgia, groups in a linestimulation to paresthesia into headaches transverse to the C2 and C3the back the C2 and C3 nerves to DBS: PVG or Treat nerve branchesprophylactically PAG nociceptive prevent components migraines and DBS:VPM Treat headaches neuropathic components or triggers CS: motor Treatcortex, lateral neuropathic part componenets or triggersTemporomandibular In front of ear Deliver PNS: branches Relieve jointpain stimulation to or of the neuropathic near the pain trigeminal painsite. May be nerve (V), desirable to including in avoid nerves in theGasserian lower jaw ganglia foramen DBS: PVG or Treat PAG nociceptivecomponents DBS: VPM Gives paresthesia into the face CS: motor Treatcortex, lateral neuropathic part components Failed back surgery Axialback, 1-4 Deliver SCS: T7-L1 Gives syndrome (axial leads, 4-64stimulation paresthesia into pain and electrodes where the the back andradiculopathy) patient leg and/or foot experiences pain PNS: Branch Alsotreat facet of median join pain an nerve or along neuropathies in nervesin leg the nerves in the leg DBS: PNG or Treat PAG nociceptivecomponents DBS: VPL Treat neuropathic components CS: motor Treat cortex,near neuropathic midline components Supra-orbital or Electrode DeliverSCS: C1-C3 Gives sub-orbital facial groups in a line stimulation toparesthesia into pain above or below branches of the the back of the theeye, roughly facial nerve head and neck parallel to the (VIII) DBS: PVGor Treat eyebrow PAG nociceptive components DBS: VPM Treat neuropathiccomponents CS: motor Treat cortex, lateral neuropathic part componentsArthritis Place Give nonpainful SCS: C4-C8 Gives electrodes instimulation to for upper limb paresthesia into skin with the the samenerves pain; T1-L1 the painful area same as those for hip, knee, whichmay dermatome as involved in pain ankle or foot lessen pain the painfularea pain PNS: of the Gives major arm or paresthesia into leg nerves thepainful area which may lessen pain DBS: PVG or Treat PAG nociceptivecomponents DBS: VPL Treat neuropathic components CS: motor Treat cortex,near neuropathic midline for leg components and feet Pelvic pain, and orPlace Give nonpainful SCS: T8-L1 Gives visceral organ pain electrodes instimulation to paresthesia into skin areas over painful area the painfularea any painful which may area lessen pain PNS: Pudendal Treat nerveneuropathic components DBS: PVG or Treat PAG nociceptive components DBS:VPL Treat neuropathic components CS: motor Treat cortex, nearneuropathic midline for components lower body Angina, heart Electrodesover Reduce angina SCS: C1-T4 Gives dysfunction, or the heart partattacks paresthesia into arrhythmia of the thorax or the painful area atany painful which may area, even in lessen pain and the arms, jaw,reduce angina or back PNS: Vagus Slows heart, nerve, medial reducingstress nerve, unlar on the heart nerve DBS: PVG or Treat PAG nociceptivecomponents DBS: VPL Treat neuropathic components DBS: Nuclei Lowersblood near the pressure hypothalamus or in the ventral lateral medullaCS: motor Treat cortex, several neuropathic centimeters off componentsthe midline Cancer or phantom Place Give nonpainful SCS: at a levelGives limb pain electrodes in stimulation to appropriate to paresthesiainto skin areas over painful area the pain the painful area any painfulwhich may area lessen pain PNS: on a nerve Treat appropriate toneuropathic the pain components DBS: PVG or Treat PAG nociceptivecomponents DBS: VPL or Treat VBM neuropathic components CS: motor Treatcortex, at a site neuropathic appropriate for components the painfularea

Table 2 below illustrates various drugs, one or more of which may bedelivered in combination with PNFS, either alone or in combination withany of the other stimulation modalities indicated above. Drugs candelivered in combination with PNFS may allow complex or multifocal painto be better addressed by: diminishing pain by their own action(additive effect), especially if applied to specific sites (patches,intrathecal, epidural); augmenting or magnifying the benefits ofelectrical stimulation; addressing certain types or locations of pain,such as morphine for nociceptive pain, or local anesthetics to blocksome nerves.

TABLE 2 Delivery Site and Reason for Drug Mechanism Delivering OpioidLumbar intrathecal space Treat nociceptive Systemic (oral, IV, aspectsof pain fentanyl patch) Subcutaneous axial back (Permeable membranecatheter) Intracerebroventricular Intraparenchymal Local peripheraladministration δ opioid Systemic, ICV, IP, Local Synergistic withperipheral administration high frequency stimulation μ opioid Systemic,ICV, IP, Local Synergistic with peripheral administration low frequencystimulation Cannabinoid Lumbar intrathecal space Treat nociceptiveSystemic (oral, IV) aspects of pain Subcutaneous axial back (Permeablemembrane catheter) Intracerebroventricular Intraparenchymal Localperipheral administration Local anesthetic (e.g. Lumbar intrathecalAdditive effect for Bupivacaine) Epidural neuropathic pain Lumbarsympathetic chain Vertebral disc Facet joint Patch infusion into axialback subcutaneous tissue Local peripheral administration BaclofenSystemic Potentiates (GABA agonist) Lumbar intrathecal neurostimulationLocal peripheral administration Adenosine Systemic Potentiates Lumbarintrathecal neurostimulation Local peripheral administration α-adrenergic Systemic Potentiates agonists (e.g. Lumbar intrathecalneurostimulation Clonidine) Vertebral disc Additive effect for Facetjoint neuropathic pain Local peripheral administration Anti- SystemicReduce inflammatory (e.g. Patch infusion into axial inflammation NSAIDS,steroids, back SQ tissue in addition to TNFα blocker) Catheter infusioninto SQ stimulation tissue Lumbar intrathecal Lumbar epidural Vertebraldisc Facet joint Local peripheral administration Muscle relaxantSystemic Relax back Patch infusion into axial muscles in back SQ tissueaddition to Catheter infusion into axial stimulation back SQ tissueLocal peripheral administration Antidepressant Systemic Additive to ICV,IP stimulation Local peripheral administration Antiepileptic (e.g.Systemic Additive to Gabapentin) ICV, IP stimulation Lumbar intrathecalLocal peripheral administration

PNFS could also be used in conjunction with physical therapy, massagetherapy, or chiropractic therapy. Any of these therapies may be providedwith the devices and systems described herein.

FIG. 4 is a block diagram illustrating an example implantable medicaldevice for delivering PNFS and one or more other types of therapy to apatient. IMD 66 may be an embodiment of any of IMDs 14, 38 or 54, whilesleads 68 and 70 may be embodiments of any leads 16 and 17, 40 and 42,and 56 and 58. As shown in FIG. 4, IMD 66 may deliver neurostimulation,such as PNFS, via electrodes 72 of lead 68 in combination with anothertype of stimulation, such as SCS, via and electrodes 74 of lead 70. Lead68 may have electrodes on multiple surfaces, e.g., may be a dual sidedpaddle lead or a multiple level lead, as described in this disclosure.Lead 70 may be a lead as described herein or any type of known lead.

Electrodes 72 and 74 are electrically coupled to a therapy deliverymodule 78 via leads 68 and 70, respectively. Therapy delivery module 78may, for example, include an output pulse generator coupled to a powersource such as a battery. Therapy delivery module 78 may deliverelectrical pulses to patient 12 via at least some of electrodes 72 and74 under the control of a processor 76.

Processor 76 controls therapy delivery module 78 to deliver PNFS andanother type of neurostimulation according to a selected one of programgroups 82 stored in a memory 80. Specifically, processor 76 may controlcircuit 78 to deliver electrical pulses with the amplitudes, pulsewidths, frequency, or electrode polarities specified by programs 84 ofthe selected program group 82, and according to the duty cyclesspecified by the programs. In the case of drug therapy, programs 84 mayspecify the amount, concentration, and rate of drug delivery. Programs84 are also stored in memory 80.

In either case, each program group 82 may include programs 84 forperipheral neurostimulation only, another therapy only, or programs forboth peripheral neurostimulation and the other therapy. Thus, processor76 may control whether peripheral neurostimulation, another therapy, orboth are delivered at any given time through selection of one of programgroups 82. Similarly, a clinician or patient 12 using programmers 20 and26, 44 and 46, or 62 and 64 to communicate with processor 76 via atelemetry module 88 may select delivery of peripheral neurostimulation,another therapy, or both through selection of one of program group 82.

Processor 76 may control therapy delivery module 78 to deliver programs84 of a program group 82, and thus PNFS and another therapy,simultaneously. Processor 76 may control module 78 to interleavedelivery of the programs 84 of the currently selected one of programgroups 82 by delivering each successive stimulation pulse according to adifferent one of the programs. Further, the duty cycles of therespective programs 84 of the currently selected one of program groups82 may be such that processor 76 controls therapy delivery module 78 todeliver the programs in an alternating manner.

Memory 80 may also store schedules 86. Schedules 86 may define times forprocessor 76 select a particular program 84 or program group 82, andcontrol therapy delivery module 78 to deliver therapy according to thatprogram or group. A schedule 86 may cause peripheral neurostimulationand at least one other therapy to be delivered at respective times,which may include simultaneous and/or alternate delivery. A clinician orpatient may create, modify, and select schedules 86 using programmers 20or 26, or any other programmers described herein.

Through interleaved delivery of programs 84, different duty cycles orpulse rates of programs, schedules 86, and patient selection of programs84 or program groups 82, therapy delivery module 78 may deliver PNFS andat least one other therapy in a generally alternating fashion. Forexample, electrical pulses may be interleaved so as to deliver the samefrequency of electrical pulses for PNFS and the other types of therapy,but with varying amplitudes or pulse widths. As another example, apacket of pulses may be delivered to provide PNFS, with or withoutramping of amplitude from start to finish, followed by delivering apacket of pulses to provide one of the other types of therapy. As aresult, the likelihood that neural accommodation will impair theefficacy of one or more of the therapies will be reduced, while stillproviding therapy at any given time. Interleaved or alternating deliveryof PNFS and one or more other electrical stimulation therapies may alsoprevent overuse or depletion of transmitters, such as GABA-B, that aremajor inhibitory transmitters released in the dorsal horn whenelectrical stimulation produces pain relief.

In addition to program groups 82, constituent programs 84 and schedules86, memory 80 may include program instructions that, when executed byprocessor 76, cause IMD 66 and processor 76 to perform the functionsascribed to IMD 66 herein. Memory 80 may include any volatile,non-volatile, magnetic, optical, or electrical media, such as arandom-access memory (RAM), read-only memory (ROM), non-volatile RAM(NVRAM), electronically-erasable programmable ROM (EEPROM), flashmemory, or the like. Processor 76 may include any one or more of amicroprocessor, digital signal processor (DSP), application specificintegrated circuit (ASIC), field-programmable gate array (FPGA),discrete logic circuitry, or the like.

IMD 66 also includes a telemetry circuit 88 that allows processor 76 tocommunicate with clinician programmer 20, 44, 62 and patient programmer26, 46, 64. Processor 76 may receive programs to test on patient 12 fromclinician programmer 20 via telemetry circuit 88 during programming by aclinician. Processor 76 may receive programs 84, program groups 82 andschedules 86 from clinician programmer 20 via telemetry circuit 88during programming by a clinician, and later receive program, programgroup, and schedule selections or modifications made by patient 12 frompatient programmer 26 via telemetry circuit 88. In embodiments in whichpatient programmer 26 stores the program groups, rather than memory 80of IMD 66, processor 76 may receive programs or groups selected bypatient 12 from patient programmer 26 via telemetry circuit 88.

FIG. 5 is a block diagram illustrating an example clinician programmerthat allows a clinician to program PNFS and one or more other types oftherapy for a patient. As shown in FIG. 5, clinician programmer 90 is anembodiment of clinician programmers 20, 44, or 62. A clinician mayinteract with a processor 92 via a user interface 102 in order toprogram delivery of PNFS in combination with one or more other types oftherapy. User interface 102 may include a display and keypad (similar todisplay 22 and keypad 24 of programmer 20), and may also include a touchscreen or peripheral pointing devices as described above. Processor 92may also provide a graphical user interface (GUI) to facilitateinteraction with a clinician, as will be described in greater detailbelow. Processor 92 may include a microprocessor, a controller, a DSP,an ASIC, an FPGA, discrete logic circuitry, or the like.

Clinician programmer 90 also includes a memory 94. Memory 94 may includeprogram instructions that, when executed by processor 92, causeclinician programmer 90 to perform the functions ascribed to clinicianprogrammer 90 herein. Memory 94 may include any volatile, non-volatile,fixed, removable, magnetic, optical, or electrical media, such as a RAM,ROM, CD-ROM, hard disk, removable magnetic disk, memory cards or sticks,NVRAM, EEPROM, flash memory, and the like.

A clinician may program delivery of PNFS and one or more types oftherapy for patient 12 by specifying a program group 96 or program 98 totest on patient 12. The clinician may interact with the GUI and userinterface 102 in order to specify program groups or programs. Processor92 transmits the selected or specified programs to an IMB (such as IMB14, 38 or 54) for delivery to patient 12 via a telemetry circuit 104.Processor 92 may transmit program groups 96 and programs 98 created bythe clinician to IMD 14 via telemetry circuitry 104, or to a patientprogrammer (such as patient programmer 26, 46 or 64) via input/outputcircuitry 106. I/O circuitry 106 may include transceivers for wirelesscommunication, appropriate ports for wired communication orcommunication via removable electrical media, or appropriate drives forcommunication via removable magnetic or optical media.

FIG. 6 is a block diagram illustrating an example patient programmerthat allows a patient to control delivery of PNFS and one or more othertypes of therapy by an implantable medical device. As shown in FIG. 5,patient programmer 108 may be an embodiment of any patient programmers26, 46, or 64. Patient 12 may interact with a processor 110 via a userinterface 118 in order to control delivery of PNFS in combination withone or more other types of therapy. User interface 118 may include adisplay and a keypad (such as display 28 and keypad 30 of programmer26), and may also include a touch screen or peripheral pointing devicesas described above. Processor 110 may also provide a graphical userinterface (GUI) to facilitate interaction with patient 12. Processor 110may include a microprocessor, a controller, a DSP, an ASIC, an FPGA,discrete logic circuitry, or the like.

Patient programmer 108 also includes a memory 112. In some embodiments,memory 112 may store program groups 114 and programs 116 that areavailable to be selected by a patient for delivery of PNFS and one ormore other types of therapy. Memory 112 may also store schedules insimilar fashion as memory 80 of IMD 14 (FIG. 4). Memory 112 may alsoinclude program instructions that, when executed by processor 110, causepatient programmer 108 to perform the functions ascribed to patientprogrammer 108 herein. Memory 112 may include any volatile,non-volatile, fixed, removable, magnetic, optical, or electrical media,such as a RAM, ROM, CD-ROM, hard disk, removable magnetic disk, memorycards or sticks, NVRAM, EEPROM, flash memory, and the like.

Patient programmer 108 also includes a telemetry circuit 104 that allowsprocessor 110 to communicate with an IMD 14, 38, 54, and input/outputcircuitry 106 that to allow processor 110 to communicate with clinicianprogrammer 20, 44, 62. Processor 110 may receive program or programgroup selections made by patient 12 via user interface 118, and mayeither transmit the selection or the selected program or group to IMD 14via telemetry circuitry 104 for delivery of neurostimulation therapyaccording to the selected program or group. Further, processor 110 mayselect a program groups 114 or programs 116 according to a schedule 100,and may either transmit the selection or the selected program or groupto IMD 14, 38, 54 via telemetry circuitry 104 for delivery ofneurostimulation therapy according to the selected program or group.Where patient programmer 108 stores program groups 114 and programs 116in memory 112, processor 110 may receive program groups 114 and programs116 from clinician programmer 20, via input/output circuitry 106 duringprogramming by a clinician. Circuitry 106 may include transceivers forwireless communication, appropriate ports for wired communication orcommunication via removable electrical media, or appropriate drives forcommunication via removable magnetic or optical media.

FIGS. 7A-7F are timing diagrams illustrating delivery of PNSF incombination with another neurostimulation therapy according toembodiments of the invention. FIGS. 7A-7F are timing diagramsillustrating delivery of PNSF in combination with anotherneurostimulation therapy according to embodiments of the invention. SCS,PNS, DBS, and CS are examples of other types of neurostimulationtherapies that may be delivered in combination with PNFS. In general,IMD 14 (or other IMDs 38 or 54, IMD 14 is used as an example from hereon) may deliver electrical pulses according to each of the therapiessimultaneously, in an interleaved or alternating fashion, or overlappingin some degree in time. For example, each electrical stimulation therapymay have different pulse rates, duty cycles, or scheduled times fordelivery, or IMD may deliver programs of a program group in aninterleaved fashion, each of which may result in an alternating deliveryof the therapies. In each of FIGS. 7A-7E, the bottom group of pulsesrepresents delivery of PNFS pulses by IMD 14, and the top group ofpulses represents delivery of another neurostimulation therapy, such asSCS, by the IMD. In FIG. 7F, the top group of pulses represents deliveryof PNFS pulses by IMD 14, and the bottom group of pulses representsdelivery of another neurostimulation therapy, such as DBS, by the IMD.Each group of pulse may represent delivery of pulses by IMD 14 accordingto a respective therapy program, and both groups of pulses may beincluded in a common program group.

FIG. 7A illustrates simultaneous delivery of PNFS and anotherneurostimulation therapy at a common pulse rate of 50 Hz by IMD 14.However, the PNFS and other neurostimulation are delivered withdifferent amplitudes and pulse widths. Specifically, in the exampleillustrated by FIG. 7A, pulse for the other neurostimulation isdelivered with a pulse amplitude and pulse width of 3 volts and 150 μs,respectively, and PNFS pulses are delivered at a pulse amplitude andpulse width of 2 volts and 300 μs, respectively.

FIG. 7B illustrates interleaved delivery of PNFS and anotherneurostimulation therapy by IMD 14 at the common pulse rate anddifferent pulse amplitudes and widths illustrated by FIG. 7A.Interleaved delivery of PNFS pulses and pulses for the otherneurostimulation resulting in a phase offset represented by a time T.

As was the case with FIG. 7B, FIG. 7C illustrates interleaved deliveryof PNFS and another neurostimulation therapy by IMD 14 at the commonpulse rate and different pulse amplitudes and widths illustrated by FIG.7A. However, in the example illustrated by FIG. 7C, IMD 14 delivers PNFSwith according to a duty cycle, rather than continuously. As a result,PNFS and the other neurostimulation are delivered for in an interleavedfashion similar to FIG. 7B for a period of time, followed by an equalperiod of time in which only the other neurostimulation is delivered.

FIG. 7D illustrates delivery of both PNFS and the other neurostimulationaccording to respective duty cycles, where the duty cycles result inalternating delivery of PNFS and the other neurostimulation.

FIG. 7E illustrates an example in which IMD 14 increases, e.g., “rampsup,” the pulse amplitude of PNFS over time. In particular, FIG. 7Eillustrates a pulse amplitude increase every two pulses

FIG. 7F illustrates delivery of PNFS and another neurostimulationtherapy by IMD according to different therapy parameters. In particular,IMD 14 delivers pulses for PNFS (top) at a frequency, amplitude, andpulse width of 40 Hz, 4.8 volts, and 400 μs, respectively, and pulse forthe other neurostimulation therapy (bottom) at a frequency, amplitude,and pulse width of 240 Hz, 2 volts, and 60 μs, respectively.

FIGS. 8A-8C, 9A-9E and 10A-10D illustrate various embodiments ofimplantable medical leads with electrodes on multiple surfaces. Suchelectrodes may be used for delivery of PNFS as described herein, e.g.,may be coupled to an IMD and extend from the IMD such that electrodes onthe lead is located within a region in which the patient experiencespain. Such leads may allow PNFS to be delivered to a larger area, andmay provide programming flexibility to a clinician for selectivestimulation of various tissues or tissue layers proximate to varioussurfaces of the lead. The invention is not limited to the illustratedleads and, as discussed above, may be implemented using any type oflead.

FIGS. 8A-8C are schematic diagrams illustrating a top and side views ofexample implantable medical leads having a plurality of electrodeslocated on more than one surface of the lead. More particularly, FIGS.8A-8C illustrate examples of dual sided paddle leads. Such leads may beused in any of the systems described above with respect to FIGS. 1-3 to,for example, deliver PNFS.

FIGS. 8A and 8B are schematic diagrams illustrating a top and a sideview, respectively, of dual sided paddle lead 124. FIG. 8B illustrateslead 124 implanted within tissue 132 of patient 12. Dual sided paddlelead 124 may be implanted in intra-dermal, deep dermal, or subcutaneoustissue of the patient.

Dual sided paddle lead 124 includes a lead body 126 carrying electrodes128A-H (collectively referred to as “electrodes 128”) located at itsdistal end. Lead body 126 may be designed similar to a paddle leaddesign known in the field of nerve stimulation, but, as shown, carrieselectrodes positioned on first and second surfaces 130A and 130B(collectively “surfaces 130”), e.g., the illustrated opposing,substantially parallel, top and bottom surfaces, instead of only on onesurface. Lead body 126 has a substantially flat, paddle-like shape,e.g., has a substantially oblong or rectangular cross-sectional shape.

As shown in FIG. 8B, electrodes 128A-D are positioned on top surface130A of lead body 126 and electrodes 128E-H are positioned on the bottomsurface 130B of lead body 126. Electrodes 128A-H (collectively“electrodes 128”) may extent above surfaces 130, may be recessedrelative to the surfaces 130, or may be co-planar with the surfaces.Electrodes 128 may be electrically insulated from each other.

In the illustrated example of FIGS. 8A and 8B, dual sided paddle lead124 includes eight electrodes, i.e., electrodes 128, positioned on thetop and bottom surfaces of lead body 126 for purposes of illustration.However, dual sided paddle lead 124 may include a lesser or greaternumber of electrodes. A dual sided paddle lead having numerouselectrodes may be particularly advantageous because the number ofelectrode possible combinations increases with the number of electrodescarried by the lead. In other words, providing a large number ofelectrode combinations increases the likelihood of discovering anelectrode combination that achieves a high clinical efficacy withminimal side effects and favorable power consumption characteristics.

Electrodes 128 are arranged in a linear array along substantially theentire length of the top and bottom surfaces 130 of lead body 126.However, the invention is not limited as such. Rather, electrodes 128may also be arranged in a two-dimensional array or any other regularlyor irregularly spaced pattern, and may be distributed in discrete groupsor “clusters,” or be distributed substantially evenly over substantiallythe entirety of surfaces 130. FIGS. 9A-E illustrate variousconfigurations of electrodes for dual sided paddle leads. In any case,each of electrodes 128 may be electrically coupled to an IMD (notshown), such as IMD 14 of FIG. 1, via a separate electrical conductor(not shown). The electrical conductors may reside in lead 124, wherethey may be electrically insulated and protected from body fluids.

The IMD may select one or more of electrodes 128 for electrodecombinations to deliver stimulation to a patient as described in FIG. 1.With respect to FIG. 8B, electrodes 128 carried by dual sided paddlelead 124 deliver neurostimulation to tissue 132. In particular,electrodes 128A-D may deliver neurostimulation to tissue 134A locatedshallower than lead 124 and electrodes 128E-H may deliverneurostimulation therapy to tissue 134C located deeper than lead 124.For example, dual sided paddle lead 124 may be implanted between deepdermal tissue layer 134B and subcutaneous tissue layer 134C, and maystimulate nerves and/or tissue in both deep dermal tissue layer 134B andsubcutaneous tissue layer 134C, as well as tissue within inter-dermaltissue layer 134A.

However, the invention is not limited as such. Rather, dual sided paddlelead 124 may be implanted within or between any of the intra-dermal,deep dermal, or subcutaneous tissue, or within any tissue or tissuelayer of a patient. The thickness of dual sided paddle lead 124, e.g.,the distance between electrodes 128A-D and electrodes 128E-H, may bevaried or selected depending on various design parameters, such as thetissues or layers for which stimulation is desired, as well as theanticipated proximity of lead 124 to such tissues or layers. Further,the depth of different layers of tissue of the patient may varydepending on the anatomy of the patient, e.g., layers of tissue of anobese patient may be thicker than those of a slender patient.

In other embodiments in which lead body 126 is implanted within aparticular tissue layer, such as deep dermal layer 134B, the thicknessof lead 124 may also affect the degree of neurostimulation delivered tothat layer. For example, if the thickness of lead 124 is sufficientlylarge, tissue 134B may not be substantially stimulated. However, thethickness of lead 124 may be sufficiently small that tissue 134B isstimulated to some degree. As a result, dual sided paddle lead 124 maybe configured to stimulate substantially distinct layers of tissue.

Further, IMD 14 may selectively deliver stimulation via a variety ofcombinations of electrodes 128. Based on the electrodes within thecombination and their polarity, as well as other stimulation parameterssuch as amplitude, IMD 14 may generate a current field via the selectedelectrodes that stimulates desired tissues or layers. IMD 14 may deliverstimulation via combinations of electrodes 128 on a single surface 130to stimulate one or more layers of tissue proximate to that surface, orcombinations that include electrodes 128 on both surfaces 130. Further,IMD 14 may simultaneously or alternatingly deliver stimulation viacombinations of electrodes 128 from respective surfaces 130, tosimultaneously or alternatingly stimulate layers above or below leadbody 126.

In the illustrated example of FIG. 8B, electrodes 128A and 128B may beselected as the first electrode combination and electrodes 128F and 128Gmay be selected as the second electrode combination. Accordingly, acurrent flow is shown between electrodes 128A and 128B and electrodes128F and 128G in FIG. 8. In such embodiments, the first electrodecombination may deliver electrical stimulation in accordance with afirst set of stimulation parameters and the second electrode combinationmay deliver electrical stimulation in accordance with a second set ofstimulation parameters. For time-interleaved delivery, stimulationpulses may be delivered in an overlapping or non-overlapping manner,such that stimulation pulses delivered to different selected electrodesets are delivered in respective overlapping or non-overlapping timeslots. In any case, the effect resulting from electrical stimulation,i.e., relief from pain or paresthesia, depends on the positions andpolarities of the electrodes and the parameters associated with thestimulation pulses.

FIG. 8C is a schematic diagram illustrating a side view of anotherexample dual sided paddle lead 136 implanted within tissue 132 ofpatient 12. Similar to dual sided paddle lead 124, dual sided paddlelead 136 includes a lead body 33 located at its distal end. Like lead124, dual sided paddle lead 136 may also include electrodes 140A-Dlocated on a first lead body surface 142A, and electrodes 140E-H locatedon a second lead body surface 142B.

However, in contrast to dual sided paddle lead 124, electrodes 140A-Dare electrically coupled to corresponding ones of electrodes 140E-H, asillustrated by the dotted line in FIG. 8C. Any number of electrodes140A-H on either of surfaces 142A and 142B may be electrically coupledsuch that they will deliver stimulation at the same time and with thesame electrical characteristics, e.g., according to the same program. Inthe illustrated example, current flows from coupled electrodes 140C and140G, which are act as cathodes on respective ones of surfaces 142A and142B, to coupled electrodes 140B to 140F, which act as anodes.

Such coupling may reduce the programming flexibility of lead 136 byproviding fewer different combinations of electrodes 140A-H that may beselected by a clinician. Further, where electrodes 140A-H on differentsurfaces 142A and 142B are electrically coupled, the ability of IMD 14to deliver stimulation via either surface to particular layers ortissues may be limited or eliminated. However, a lead with fewerconductors may be more cost effective to manufacture, more flexible, andless prone to failure due to, for example, fracturing or degradation ofthe conductors. Further, in some embodiments, simultaneous delivery ofstimulation to a large tissue region may be preferred over selectabilityof tissues or layers. If electrodes are near to the edge of a dual sidedpaddle, currents may be programmed to flow between two or moreelectrodes on opposite side of the paddle, giving the greatest possiblespread of current beyond the edge of the paddle.

FIGS. 9A-9E are schematic diagrams illustrating top views of otherexample implantable medical leads having a plurality of electrodeslocated on more than one surface of the lead. FIGS. 9A-9E are schematicdiagrams illustrating top views of example dual sided paddle leads. Inparticular, FIG. 9A is a top view of dual sided paddle lead 144 having asquare shaped lead body 146 and FIG. 9B is a top view of dual sidedpaddle lead 150 having a circular shaped lead body 152. The circularshape of lead body 152 may require substantial dissection forimplantation within patient 12, but may provide a form factor that bestcovers the patient's perceived region of pain. In contrast, the squareor rectangular shape of lead body 146 is characterized by asubstantially smaller width than lead body 152 and, thus, may reduce theamount of tissue damage caused during implantation. The illustratedsurfaces of lead bodies 146 and 152 respectively include electrodes148A-D and electrodes 154A-D. At least one other surface of lead bodies146 and 152, such as an opposing or bottom surface not shown in FIGS. 9Aand 9B, includes additional electrodes.

FIGS. 9A and 9B are merely exemplary and should not be consideredlimiting of the invention as broadly described in this disclosure. Forexample, a dual sided paddle lead as described in this disclosure mayhave a leady body that is circular, rectangular, square, round, oval, orany other uniform or non-uniform shape. Accordingly, the lead body maybe shaped to match the patient's perceived region of pain, to reduce theamount of tissue damage cause during implantation, or achieve a tradeoffof these design parameters. Further, lead body shapes illustrated inFIGS. 9A and 9B are not limited to dual sided paddle leads. Rather,separate lead body levels of a multiple level lead, as will be describedbelow, may have the illustrated shapes.

FIGS. 9C-E are schematic diagrams illustrating top views of otherexample dual sided paddle leads with various configurations ofelectrodes. However, the configurations of electrodes illustrated inFIGS. 9C-E are not limited to dual sided paddle leads. Rather, theconfigurations of electrodes illustrated in FIGS. 9C-E may also be usedwith multiple level leads described in this disclosure.

FIG. 9C is a top view of a dual sided paddle lead 156 having anelongated lead body 158 located at the distal end of the lead. Lead body158 carries a two dimensional array of electrodes 159A-F (collectivelyreferred to as “electrodes 159”) on its top surface. A two-dimensionalarray generally refers to an ordering of electrodes along at least twodifferent lines, e.g., as rows and columns. As shown in FIG. 9C,electrodes 159 are arranged in two evenly spaced rows that are staggeredrelative to each other. Alternatively, electrodes may be positionedirregular intervals within a line or at positions that do not representan ordered pattern. In some embodiments, a two-dimensional array ofelectrodes may comprise electrodes arranged in three or more rows.

FIG. 9D is a top view of a dual sided paddle lead 160 having anelongated lead body 164 located at the distal end of the lead. Lead body164 carries a linear array of electrodes 162A-D (collectively referredto as “electrodes 162”) on its top surface. A linear array generallyrefers to an ordering of electrodes along a common line. In theillustrated example of FIG. 9D, electrodes 162 are arranged along thelongitudinal axis of lead body 164 at regular intervals and are offsetfrom each other rather than being in line with the longitudinal axis.

FIG. 9E is a top view of a dual sided paddle lead 166 having a circularshaped lead body 168 located at the distal end of the lead. Lead body168 carries electrodes 170A-H (collectively referred to as “electrodes170”) on its top surface. Electrodes 170 are arranged in an orderedpattern about the circumference of lead body 168 with regular spacing.The number of electrodes shown in FIG. 9E is merely exemplary. Anynumber of electrodes may be arranged in an ordered pattern or,alternatively, at positions that do not represent an ordered pattern. Inany case, the number and pattern of electrodes may be selected based onthe patient's perceived region of pain.

FIGS. 10A-10D are schematic diagrams illustrating side views of otherexample implantable medical leads with electrodes positioned on varioussurfaces. FIGS. 10A-D are schematic diagrams illustrating side views ofexample multiple level leads implanted within tissue 174. Each of FIGS.10A-D illustrates a multiple level lead with electrodes positioned onvarious surfaces to selectively deliver stimulation to layers of tissuelocated proximate to or between adjacent levels of the lead. A multiplelevel lead may be implanted within intra-dermal, deep dermal, orsubcutaneous tissue of a patient and includes one or more electrodespositioned on at least one surface of each level of the lead.

Each of the multiple level leads illustrated in FIGS. 10A-D include alead body with two lead body levels, i.e., an upper level and a lowerlevel. Each of the lead body levels may have a substantially flat,paddle-like shape, as described above with reference to paddle leads 124and FIGS. 8A-C. However, the invention is not so limited. Rather, amultiple level lead may include any number of lead body levels with anyshape, even a simple cylindrical shape with a round cross section. Inthe interest of brevity, FIGS. 10A-D illustrate the variousconfigurations for a multiple level lead having two levels. A multiplelevel lead having more than two levels follows from the descriptionprovided in this disclosure. Accordingly, FIGS. 10A-D are merelyexemplary and should not be considered limiting of the invention asbroadly described in this disclosure.

FIG. 10A illustrates multiple level lead 176 implanted within tissue 174of patient 12. Multiple level lead 176 includes a lead body 182 at itsdistal end comprising an upper lead body level 178A and a lower leadbody level 178B (collectively “levels 178”). Upper level 178A may belocated closer to the surface of the skin of patient 12 than lower level178B. Upper level 178A carries electrodes 180A-D on its top surface andlower level 178B carries electrodes 180E-H on its bottom surface. Inthis manner, multiple level lead 176 carries electrodes 180A-H(collectively “electrodes 180”) on opposite surfaces of adjacent levelssuch that electrodes 180A-D and electrodes 180E-H face away from eachother.

In the illustrated example of FIG. 10A multiple level lead 176 includeseight electrodes for the purposes of illustration. However, aspreviously described with respect to dual sided paddle leads in FIGS. 8Aand 8B, multiple level lead 176 may include a lesser or greater numberof electrodes. Again, having numerous electrodes may be particularlyadvantageous because the number of electrode possible combinationsincreases with the number of electrodes carried by the lead. In otherwords, providing a large number of electrode combinations increases thelikelihood of discovering an electrode combination that achieves a highclinical efficacy with minimal side effects and favorable powerconsumption characteristics.

Electrodes 180A-D and 180E-H may be arranged in any regular or irregularpattern such as those illustrated in or described with respect to FIGS.9A-E. For example, electrodes 74A-D and 74E-H may be arranged in thesame pattern, such as the two-dimensional array illustrated in FIG. 9C,or may be arranged in different patterns, such as the two-dimensionalarray illustrated in FIG. 9C and the linear array illustrated in FIG.9D. In any case, each of electrodes 180A-D and 180E-H may beelectrically coupled to an IMD (not shown), such as IMD 14 of FIG. 1,via a separate electrical conductor (not shown) within lead 176.

In operation, the IMD may apply stimulation across selected electrodesof 180A-D and 180E-H to deliver, for example, PNFS to various layers oftissue 174. In particular, one or more of electrodes 180A-D may deliverstimulation to tissue 181A located shallower than upper level 178A andone or more of electrodes 180E-H may deliver stimulation therapy totissue 181C located deeper than lower level 178B. In one example,multiple level lead 176 may be implanted in deep dermal tissue 181B andmay stimulate nerves and/or tissue in both intra-dermal and subcutaneoustissue 181A and 181C, respectively. However, the invention is notlimited as such and multiple level lead 176 may be implanted inintra-dermal, deep dermal, or subcutaneous tissue. Regardless of whichlayer of tissue multiple level lead 176 is implanted, multiple levellead may deliver stimulation to a layer of tissue located shallower thanupper level 178A and a layer of tissue located deeper than lower level178B.

However, the distance between upper level 178A and lower level 178B maybe selected based on one or more design parameters. For example, thedistance between upper level 178A and lower level 178B may be selectedin a similar manner to selecting the thickness of a dual sided paddlelead, as described with respect to dual sided paddle lead 124 in FIGS.8A and 8B. In particular, the distance may be selected such that upperlead body 180A and lower lead body 180B are implanted within distinctlayers of tissue, such as intra-dermal and subcutaneous tissue,respectively. In this case, the distance may vary depending on theanatomy of the patient, e.g., layers of tissue of an obese patient maybe thicker than those of a slender patient.

The distance may also affect the degree of stimulation delivered totissue 181B, i.e., the layer of tissue in which multiple level lead 176is implanted. For example, if the distance between upper level 178A andlower level 178B is sufficiently large, neurostimulation may only bedelivered to tissue 181A and 181C. In other words, tissue 181B may notbe substantially stimulated. In contrast, however, the height may besufficiently small such that tissue 181B is stimulated to some degree.

Again, multiple level lead 176 may deliver stimulation, such as PNFS, totissue 181A and 181C at the same time or in an alternating orinterleaved fashion. For example, a first electrode combination selectedfrom electrodes 180A-D may deliver PNFS to tissue 181A and a secondelectrode combination selected from electrodes 180E-H may deliver PNFSto tissue 181C. Accordingly, a current flow is shown between electrodes180C and 180D and electrodes 180F and 180G in FIG. 10A. In suchembodiments, the first electrode combination may deliver electricalstimulation in accordance with a first set of stimulation parameters andthe second electrode combination may deliver electrical stimulation inaccordance with a second set of stimulation parameters. Fortime-interleaved delivery, stimulation pulses may be delivered in anoverlapping or non-overlapping manner, such that stimulation pulsesdelivered to different selected electrode sets are delivered inrespective overlapping or non-overlapping time slots. In any case, theeffect resulting from electrical stimulation, i.e., relief from pain orparesthesia, depends on the positions and polarities of the electrodesand the parameters associated with the stimulation pulses.

FIG. 10B is a side view illustrating multiple level lead 184 implantedwithin tissue 174 of patient 12. Similar to multiple level lead 176,multiple level lead 184 includes a lead body 190 with an upper lead bodylevel 186A and a lower lead body level 186B (collectively “levels 186”).However, in contrast to multiple level lead 176, upper level 186Acarries electrodes 188A-D on its bottom surface and lower lead bodylevel 186B carries electrodes 188E-H on its top surface. As a result,multiple level lead 184 carries electrodes 188A-D and 188E-H on adjacentsurfaces of adjacent levels such that electrodes 188A-D and 188E-H faceeach other.

Consequently, multiple level lead 184 may focus delivery of stimulationto tissue, such as layer 181B, located between adjacent levels 186. Withreference to the example illustrated by FIG. 10B, multiple level lead184 may be able to deliver stimulation to tissue 181B withoutsubstantially stimulating tissue 181A located superior to upper level186A or tissue 186C located inferior to lower level 186B. Upper level186A and lower level 186B may electrically isolate tissue 181A and 181Cfrom being stimulated by neurostimulation delivered to 181B. Again,tissues 181A, 181B and 181C may correspond to intra-dermal, deep dermaland subcutaneous tissue layers within a region 19, and the IMD maydeliver PNSF via lead 184.

In some embodiments, as illustrated by the labeled current flow in FIG.10B, an IMD may apply electrical stimulation pulses across electrodes188A-H such that an anode and cathode are not on the same level.However, the invention is not so limited. An IMD may deliver stimulationto tissue between levels 186 via any combination of electrodes 188A-H onone or both of the levels.

FIG. 10C is a side view illustrating another example multiple level lead192 implanted within tissue 174 of patient 12. Again, multiple levellead 192 is similar to multiple level leads 176 and 184 with respect tophysical structure, i.e., multiple level lead 192 includes a distal leadbody 198 with an upper level 194A and a lower level 194B. However,unlike multiple level leads 176 and 184, upper level 194A carrieselectrodes 196A-D on its bottom surface and lower level 194B carrieselectrodes 196E-H on its bottom surface. As a result, multiple levellead 192 delivers neurostimulation to tissue 181B located between upperlevel 194A and lower lead level 194B and tissue 181C located deeper thanlower lead body 194B.

In particular, multiple level lead 192 may deliver neurostimulation,such as PNFS, to tissue 181B and 181C without substantially stimulatingtissue 181A. In operation, the IMD (not shown) coupled to multiple levellead 192 may apply electrical stimulation pulses across one or more ofelectrodes 196A-D and one or more of electrodes 196E-H to stimulatetissue 181B and tissue 181C, respectively. In this case, the IMD mayselect anode and cathode on the same level. As an example, FIG. 10Cillustrates a current flow between electrodes 196C and 196D to stimulatetissue 181B and between electrodes 196G and 196H to stimulate tissue181C. When delivering neurostimulation to tissue 181B and 181C, upperlevel 194A may substantially electrically isolate tissue 181A from beingstimulated by neurostimulation delivered to tissue 181B and tissue 181C.

FIG. 10D is a side view illustrating multiple level lead 200 implantedwithin tissue 174 of patient 12. Multiple level lead 200 is similar tomultiple level leads 176, 184, and 192 with respect to physicalstructure, i.e., multiple level lead 200 includes a distal lead body 206with an upper level 202A and a lower level 202B. However, unlikemultiple level leads 176, 184, and 192, upper level 202A carrieselectrodes 204A-D on its top surface and electrodes 204E-H on its bottomsurface, and lower level 202B carries electrodes 204I-L on its topsurface and electrodes 204M-P on its bottom surface. As a result,multiple level lead 200 may selectively deliver neurostimulation to anyone or more of tissue 181A, 181B, and 181C.

Each of electrodes 204A-P are electrically isolated from each other and,thus, electrode combinations may be selected to deliver stimulation,such as PNFS, to any desired one or more of tissue layers 181A, 181B,and 181C. However, in other embodiments, electrodes on differentsurfaces of the levels may be electrically coupled in the mannerdiscussed above with reference to FIG. 8C. Such coupling may simplifythe structure and manufacturing of a multiple level lead.

FIG. 11 is a schematic diagram illustrating a lead 216 that includesfixation structures. Lead 216 includes a lead body 206 at its distal endthat carries electrodes 220A-H (collectively referred to as “electrodes220”) on multiple surfaces. Lead 216 may be a dual-sided paddle lead inwhich lead body 206 has a substantially flat, paddle-like shape, and maybe substantially similar to dual sided paddle lead 124 of FIGS. 8A and8B. However, unlike dual sided paddle lead 124, dual sided paddle lead216 includes fixation structures 222A and 222B for securing lead 216that prevent lead 216 from migrating from the implantation site.

Fixation structures may protrude from lead body 206 to engage tissueproximate to the lead body, as illustrated in FIG. 11. Fixationstructure 222 may comprise one or more of tines, barbs, hooks, activelyor passively deployable fixation structures, or collapsible orexpandable fixation structures. Fixation structures may includetitanium, stainless steel, nitinol, hydrogel, or any of a variety ofmaterials. Tines, barbs and hooks may pierce tissue proximate to lead216 to prevent migration after implantation. Tissue ingrowth surroundingtines or barbs may further secure lead 216. Not shown, the tines, barbsand hooks may lie in the plane of the paddle.

When not acted upon by a force, collapsible structures assume anexpanded configuration with the fixation structures extending away fromlead body 206. However, when inserted into an insertion device, such asa needle, the collapsible fixation structures move close to lead body218 assuming a collapsed configuration. When lead 216 is expelled fromthe insertion device, the fixation structures move toward their expandedpositions.

Actively deployable fixation structures may include one or more activelydeployable clips which, upon deployment, provides fixation of the leadto tissue proximate to the lead. The clip may be deployed in a varietyof ways, such as releasing the clip from a restraint using a surgicaltool or releasing the clip upon passage of the lead through body tissueto prevent withdrawal of the lead from body tissue. In this manner,protruding fixation structures 222A and 222B may enable a lesscomplicated and time consuming method for securing a paddle lead, suchas dual sided paddle lead, a multiple level lead, or a paddle lead knownin the nerve stimulation field, to tissue to prevent migration. Otherembodiments may include any type of fixation mechanism used to fixcardiac leads.

In some embodiments, dual sided paddle lead 216 may only includeprotruding fixation structures 222B or 222A, i.e., may only includeprotruding fixation structures on a distal or a proximal end.Accordingly, FIG. 6 is merely exemplary and should not be consideredlimiting of the invention as broadly described in this disclosure. Forexample, protruding fixation structures 222A and 222B may be implementedwith paddle leads that include electrodes on only a single surface.Protruding fixation structures located at the distal end of such paddleleads may offer similar advantages as described with respect to dualsided paddle lead 216. Further, fixation structures may be provides onmultiple level leads as described herein.

FIG. 12 is a conceptual diagram illustrating another example system thatdelivers PNFS in combination with at least one other therapy. Moreparticularly, FIG. 12 illustrates a system 226 that includes multiplemedical devices for delivering PNFS and the at least one other therapy.In the illustrated example, system 226 includes a first IMD 234 thatdelivers PNFS to a region in which a patient 228 experiences pain, and asecond IMD 236 that delivers the at least one other therapy.

Through delivery of a combination therapy that includes PNFS and one ormore other types of therapy, system 226 may be able to more completelyaddress complex or multifocal pain than would be possible throughdelivery of either PNFS or the other therapies alone. In addition, thecombination of PNFS with one or more other types of therapy may reducethe likelihood that neural accommodation or plasticity will impair theperceived effectiveness of any of the therapies. In some embodiments, asillustrated in FIG. 12, IMDs 234 and 236 may communicate, e.g.,wirelessly via radio frequency or body conduction, to coordinate thedelivery of their respective therapies.

As illustrated in FIG. 12, IMD 234 may be configured for implantationwithin region 232, e.g., may include a relatively miniaturized housing.Further, as will be described in greater detail below, IMD 234 may havea housing with electrodes on multiple housing surfaces for delivery ofPNFS to region 232. Location of electrodes on multiple surfaces of ahousing implanted within a painful region may allow a large area andvariety of tissues to be stimulated, and may provide programmingflexibility with respect to selection tissues to be stimulated, asdescribed above with respect to the implantable medical leads of FIGS.8A-10D.

However, the invention is not limited to embodiments in which IMD 234 isimplanted within an axial back region as illustrated in FIG. 12. Inother embodiments, IMD 234 may be implanted in the face, head, chest,stomach, pelvis, or limbs of patient 228 for delivery of PNFS to aregion in which the patient experiences pain. Moreover, the invention isnot limited to embodiments in which IMD 234 includes housing electrodes,or is implanted within region 232. In other embodiments, IMD 234 may becoupled to a lead that extends to a region in which patient 232experiences pain.

In the illustrated embodiment, additional IMD 236 delivers spinal cordstimulation (SCS) to the spinal cord 230 of patient 228 in combinationwith delivery of PNFS. IMD 236 delivers SCS via electrodes located onone or more leads 238 implanted proximate to spinal cord 230. IMD 236may deliver SCS to any of the spinal cord regions and for any of thepurposes described above with respect to FIGS. 1-3.

However, the invention is not limited to embodiments in which lead 238extends to spinal cord 230, or IMD 236 delivers SCS. In otherembodiments, an IMD may deliver one or more of PNS, DBS or CS via leadsextending to appropriate positions proximate to target nerves, or on orwithin the brain, as described above with reference to FIGS. 1-3.Further, the invention is not limited to embodiments in which the othertherapy that treats pain is a type of neurostimulation. In someembodiments, for example, IMD 236 may deliver a drug or othertherapeutic agent in combination with the PNFS delivered by IMD 234. Insuch embodiments, IMD 236 may include a reservoir and pump, and becoupled to a catheter that extends to a target location for delivery anyof a variety of therapeutic agents, as described above with reference toFIGS. 1-3.

Also, the invention is not limited to IMDs, for example, an externaldevice may deliver a therapy, such as transcutaneous electricalneurostimulation (TENS), in combination with the delivery of PNFS by IMD234. Moreover, other delivery mechanisms, such as a patch or othertransdermal delivery mechanism, or oral consumption by a patient, may beused for a combination therapy including a therapeutic agent. Forexample, patient 228 may absorb drugs through a patch at region 232 tofurther relieve pain experienced at region 232 or enhance the PNFStherapy. As one example of the synergy between therapies, PNFS deliveredto region 232 by IMD 234 may reduce allodynia, thereby allowing a patchto be applied to the skin of patient 228 to deliver drug therapy.Similarly, PNFS may sufficiently reduce allodynia so that a TENSelectrode can be applied to the skin.

System 226 may deliver PNFS in combination with other types of therapysimultaneously, or in an interleaved or alternating fashion, asdescribed above. For example, when the combined therapies include aplurality of electrical stimulation therapies, IMDs 234 and 236 maydeliver electrical pulses according to each of the therapies in analternating or interleaved fashion, e.g., each pulse delivered accordingto a different one of the therapies. Consequently, the delivery of eachtherapy can be optimized at each site. Clinician and patient programmers240 and 242 may be substantially similar to the programmers discussedabove, and may be used to program or control delivery of therapy by eachof IMDs 234 and 236 via telemetry in the manner discussed above withreference to programming of a single IMD and FIGS. 1-6.

FIGS. 13A and 13B are schematic diagrams respectively illustrating topand side views of the implantable medical device of FIG. 12 withelectrodes located on a top surface and a bottom surface of theimplantable medical device housing. As illustrated in FIGS. 13A and 13B,IMD 234 includes a housing 246 with a top surface 248A and a bottomsurface 248B. IMD 244 also includes a plurality of electrodes 252. Afirst subset of electrodes 252 is located on top surface 248A, while asecond subset of electrodes 252 is located on bottom surface 248B.

IMD 234 may deliver electrical stimulation, e.g., pulses, via a selectedcombination of electrodes 252 from one or both of top surface 248A andbottom surface 248B. When IMD 234 is implanted within or between one ormore of the inter-dermal, deep dermal, and/or subcutaneous tissuelayers, the subsets of electrodes 252 on the housing surfaces 248 may berespectively located more proximate to different ones of the layers. Theability of a clinician to select electrodes 252 from one or both ofhousing surfaces 248 for an electrode configuration for a stimulationprogram, may allow the clinician to select a current field configurationthat stimulates a desired one or more of the tissue layers. In otherwords, an IMD 244 with electrodes 252 located on multiple housingsurfaces 248 according to the invention may selectively stimulate anyone or more tissue layers.

As illustrated in FIG. 13B, top and bottom housing surfaces 248A and248B (collectively “housing surfaces 248”) may be substantiallyparallel, opposing, major surfaces of housing 246. A “major” surface ofa housing has a relatively large surface area when compared to othersurfaces. For example, top and bottom housing surfaces 248 are majorsurface in that they have a relatively large surface area when comparedto the side surfaces of housing 246. While electrodes 252 are shownlocated on opposing, substantially parallel surfaces 248 of housing 246,electrodes 252 may be located on adjacent surfaces of the housing, e.g.,top surface 248A and one of the side surfaces of housing 246. In somealternative embodiments, electrodes 252 may be located on three or moresurfaces of housing 246. Electrode areas or spacing might have to beoptimized depending on the tissue stimulated, e.g., skin versus muscle.

In the example illustrated by FIG. 13A, electrodes 252 are distributedover substantially the entire length of top surface 248A. Further,electrodes 252 are arranged in a row substantially along an axis 250 oftop surface 248A. However, the invention is not limited to theillustrated arrangement of electrodes 252, or any particular arrangementof electrodes. For example, electrodes may be arranged on surfaces inmultiple rows substantially parallel to axis 250, in a substantially“checkerboard-like” pattern, or a substantially irregular pattern.Further, electrodes 252 may be distributed across substantially theentirety of one or both of surfaces 248, or may be grouped into one ormore discrete clusters at various positions on the surface.

Moreover, the number, size and shape of electrodes 252 illustrated inFIGS. 13A and 13B are merely exemplary. IMD 234 may include as few as asingle electrode 252 on each of housing surfaces 248. Further, althoughillustrated as substantially flat electrode pads with substantiallycircular cross-sectional shapes, electrodes 252 may have any two orthree-dimensional shape.

FIGS. 14A and 14B are schematic diagrams respectively illustrating topand side cross-sectional views of IMD 234. As shown in FIGS. 14A and14B, housing 246 of IMD 244 houses a control module 258, a battery 256,and a coil 254 encircling control module 258. In some embodiments, coil254 may encircle control module 258, battery 256, or both.

Control module 258 receives power from battery 256 to drive theelectrodes 24 according to one or more stimulation programs, which maybe stored within control module 258 and/or received from one ofprogrammers 240, 242, e.g., via radio frequency (RF) or inductivetelemetry. Control module 258 may include control electronics, such asany one or more of a microprocessor, DSP, ASIC, FPGA, or other digitallogic circuitry. Control module 258 may also include memory, such as anyone or more of ROM, RAM, NVRAM, EEPROM, or flash memory. The memory ofcontrol module may store stimulation programs, as well as programinstructions that, when executed by the control circuitry of controlmodule 258, cause control module 258 and IMD to provide thefunctionality ascribed to them herein. Control module 258 may alsoinclude stimulation generation circuitry, such as voltage or currentpulse generators that include capacitors, regulators, current mirrors,or the like, as is known in the art.

Battery 256 may be rechargeable, and may have a capacity of at least 20milliamp-hr, more preferably at least 25 milliamp-hr, and still morepreferably at least 30 milliamp-hours. In this case, battery 256comprises a capacity almost an order of magnitude larger thanconventional microstimulators. In some embodiments, battery 256 maycomprise a lithium ion rechargeable battery.

Coil 254 may serve as a telemetry coil for wireless communication withan external programmer, e.g., programmers 240 and 242. Coil 254 may beformed of windings of copper or another highly conductive material. Insome embodiments in which battery 256 is rechargeable, coil 254 may alsoact as an inductive power interface to recharge battery 256, e.g., mayinductively receive energy from an external recharging unit (notillustrated) through the skin of patient 228 to recharge battery 256. Inother embodiments, separate coils may be provided for communication andrecharging.

Further, the invention is not limited to embodiments in which battery256 is rechargeable, or in which IMD 244 includes a battery. Forexample, IMD 234 may include a non-battery power source, such as asupercapacitor. In other embodiments, IMD 234 may not store power, andcontrol module 258 may instead receive power substantially continuouslyfrom an external source via coil 254 or another coil.

Housing 246 may be formed from any of a variety of materials such assilicone, polyurethane, other polymeric materials, titanium, stainlesssteel or ceramics. As shown in FIG. 14A, housing 246 conforms to asubstantially rectangular form factor. In alternative embodiments,housing 246 may include curved, angled, or asymmetric edges such thatthe housing fits within the implant region of the patient. Housing 246may conform to a miniaturized form factor with a low profile in order tofit within a desired layer of tissue for implant.

IMD 234 or housing 246 may have a length (L) of approximately 30 to 160mm, a width (W) of approximately 10 to 20 mm and a thickness (T) ofapproximately 3 to 6 mm. In some embodiments, IMB 234 or housing 246 mayhave a length (L) less than approximately 50 mm, and a thickness (T) ofless than approximately 6 mm. In some embodiments, IMB 234 or housing246 comprises a length (L) of less than or equal to 36.6 mm (1.44inches), a width (W) of less than or equal to 14.5 mm (0.57 inches), anda thickness (T) of less than or equal to 4.5 mm (0.177 inches). In someembodiments, IMD 234 may include approximately 0.25 mm (0.01 inches) ofinsulation between control module 258, battery 256 and housing 246. Thewalls of housing 246 may comprise a total thickness of approximately0.71 mm (0.03 inches).

Control module 258 and coil 254 are designed to be very thin and flat tofit within housing 246. For example, control module 258 may comprise alength of less than or equal to approximately 6.5 mm (0.256 inches), awidth of less than or equal to approximately 9.4 mm (0.37 inches), and athickness of less than or equal to approximately 3.6 mm (0.14 inches).Further, although battery 256 comprises a capacity almost an order ofmagnitude larger than some conventional microstimulators, battery 256has a relatively small capacity compared to full size IMDs. Therefore,coil 254 may be smaller than coils within traditional IMDs. Coil 254 maycomprise inner dimensions slightly larger than the dimensions of controlmodule 258 given above.

Coil 254 may comprise an inner length of approximately 6.7 mm (0.265inches) and an inner width of approximately 9.7 mm (0.38 inches). Theouter dimensions of coil 254 may comprise an outer length ofapproximately 8.4 mm (0.33 inches) and an outer width of approximately11.7 mm (0.46 inches). Coil 254 may also comprise a thickness ofapproximately 2.5 mm (0.10 inches).

Similarly, battery 256 may be configured to fit within the relativelythin and flat housing 246. For example, battery 256 may be a lithium ionbattery with a thin, generally flat housing or cylindrical housing. Inthe case of a pin type cell, battery 256 may have an aluminum housingwith a crimped or riveted pin feedthrough. In some embodiments, battery256 alternatively may comprise a foil pack battery.

Battery 256 may comprise a length of less than or equal to approximately24.9 mm (0.98 inches), a width of less than or equal to approximately12.7 mm (0.50 inches), and a thickness of less than or equal toapproximately 3.3 mm (0.13 inches). Battery 256 may be loaded withelectrical charge in a standard or adjustable manner, which may affectthe dimensions of possible battery dimensions. Battery 256 may conformto one of a variety of designs. Some examples are given in Table 3below.

TABLE 3 3.0 mm thick 3.0 mm thick 3.3 mm thick 3.3 mm thick standardadjustable standard adjustable loading loading loading loading Length(mm) 25.4 25.4 25.4 24.9 Width (mm) 16.5 14.2 13.2 12.7 Capacity (mA- 3030 31 30 hr) Battery Case 1.26 1.08 1.11 1.04 Volume (cc) Coating 2212.1 22 12.32 Deposition (mg/cm²)

IMD 234 may be over-discharge protected. However, since battery 256conforms to an extremely small form factor, the over-dischargeprotection may be difficult to realize using traditional approaches,such as extra battery capacity. Therefore, IMD 234 may include a switchto disconnect battery 256 from the load, e.g., an adjustable loadingbattery, when a predetermined voltage is reached. In other cases,battery 256 may comprise an over-discharge tolerant battery.

Each of electrodes 252 may be substantially circular, square orrectangular, or may have other cross-sectional shapes or substantiallyirregular cross-sectional shapes. In the case of a circularcross-sectional shape, each electrode 252 may have a diameter ofapproximately 0.5 mm to 1.5 mm, and more preferably 1 mm. IMD 234 mayinclude between 2 and 32 electrodes, although greater numbers ofelectrodes are possible. Inter-electrode distances (D) on surfaces 248may be within a range from approximately 0.1 mm to approximately 5.0 mm,and in some embodiments may be approximately to 0.5 mm.

Electrodes 252 may be distributed on each of housing surfaces 22 in alinear or a two-dimensional array. A linear array generally refers to anordering of electrodes 252 along a common line or axis, such as axis 250illustrated in FIG. 13A, whereas a two-dimensional array generallyrefers to an ordering of electrodes 252 along at least two differentlines, e.g., as rows and columns, or a checkerboard pattern. In eithercase, the array of electrodes 252 may have a regular, periodic patternsuch that electrodes are positioned at regular spatial intervals withina line, row or column.

Alternatively, the array may be irregular such that electrodes 252 arepositioned at irregular intervals or at positions that do not representan ordered pattern. Further, as discussed above, electrodes 252 need notbe located substantially along substantially the entire lengths oracross substantially the entire surface areas of housing surfaces 248.Instead, electrodes 252 may be clustered or grouped at particularlocations on the surfaces. However, distributing electrodes 252 alongsubstantially the entire length or across substantially the entiresurface area of a housing surface 248 may enable IMD 244 to selectivelystimulate tissues within a larger region, which may make it more likelythat a desirable electrode configuration and stimulation program interms of efficacy and side effects will be discovered.

FIGS. 15A and 15B are schematic diagrams respectively illustrating topand side cross-sectional views of another example implantable medicaldevice with electrodes located on multiple housing surfaces, in whichthe housing includes a bend. As shown in FIGS. 15A and 15B, IMD 260includes a housing 262 with a top surface 276A and a bottom surface276B, and electrodes 274A-C and 274D-F located on top surface 276A andbottom surface 276B, respectively. Electrodes 274A-F (collectively“electrodes 274”) may be substantially similar to electrodes 252discussed above, and arranged on surfaces 276A and 276B (collectively“housing surfaces 276”) in substantially the same manner as discussedabove with reference to electrodes 252.

Like housing 246 of IMD 234, housing 262 contains a control module 268which provides substantially the same functionality as discussed abovewith reference to control module 268 of IMD 234 and FIGS. 14A and 14B.Housing 262 also contains battery 272 and coil 270 substantially similarto battery 256 and coil 254 discussed above with reference to IMB 234.In general, housing 262 may be substantially in most respects housing246 described above with reference to IMB 234 and FIGS. 14A and 14B.

However, as illustrated in FIG. 15B, housing 262 may also comprise adegree of curvature, or angle, to conform to tissues at an implantationsite for IMD 260. Housing 262 may be formed with the angle or degree ofcurvature. In other cases, a clinician may bend housing 262 to a degreeof curvature appropriate for a specific stimulation site. For example,housing 262 may comprise a flexible material or include bellows thatallow housing 262 to bend. In other embodiments, housing 262 may includea hinge that may rotate to allow the housing to change its curvature.The hinge may include a screw or other limiting mechanism to set thehinge to a desired degree of curvature.

In the example of FIGS. 15A and 15B, housing 262 is defines an angle (A)at a boundary 264 between a portion of the housing containing controlmodule 268 and a portion containing battery 272. The angle (A) may beapproximately 20 to 40 degrees, and more preferably approximately 30degrees. Boundary 264 is illustrated in FIG. 15B as defining a sharptransition, but include a rounded curvature in other embodiments.Further, although a single boundary and angle are illustrated, IMDsaccording to the invention may include multiple boundaries and angles.

As illustrated in FIG. 15A, control module 268 comprises an applicationspecific integrated circuit, e.g., IC 268, designed to minimize thenumber of components within IMD 260. IC 268 may be designed using the0.8 micron process in an effort to reduce the overall size and profileof IMD 260. With sufficient processing power, IC 268 may have afootprint of approximately 5.2 mm (0.204 inches) by 5.2 mm and athickness of approximately 0.46 mm (0.018 inches).

IC 268 may be application specific to minimize the components needed bythe IC for operation. The ASIC may include both a battery rechargemodule and a telemetry module that couple to coil 254, as well as apulse generator and processor. The processor directs the pulse generatorto drive one or more electrodes based on stimulation programs stored inmemory accessible by the control module 268 or received by the telemetrymodule. A power management module coupled to battery 272 powers thecontrol circuitry and pulse generator within control module 268.

FIG. 16 is a schematic diagram illustrating a side cross-section view ofanother example implantable medical device 278 with electrodes locatedon multiple housing surfaces and in which the housing includes a bend.As shown in FIG. 16, IMD 278 includes a housing 280 with a top surface286A and a bottom surface 286B, electrodes 284A and 284B located on topsurface 286A, and electrodes 284C and 284D located on bottom surface286B. Electrodes 284A-D (collectively “electrodes 284”) may besubstantially similar to electrodes 252 discussed above, and arranged onsurfaces 286A and 286B (collectively “housing surfaces 286”) insubstantially the same manner as discussed above with reference toelectrodes 252. Further, IMD 278 includes a control module 290, battery288 and coil 292 within housing 280, which may be substantially similarto and provide substantially the same functionality as any of thecontrol modules, batteries and coils discussed above. Additionally, likehousing 262 discussed above with reference to FIGS. 15A and 15B, housing280 defines an angle at a boundary 282, which may be substantiallysimilar to angle (A) discussed above with reference to housing 262.

However, unlike coils 254 and 270 of IMDs 234 and 260, coil 292 of IMD278 does not substantially surround control module 290. Instead, coil292 is located between battery 288 and control module 290, proximate tothe boundary at which housing 280 is angled. Again, in variousembodiments, a coil may substantially surround a control module,battery, both the control module and the battery, or, as illustrated inFIG. 16, neither the control module nor the battery.

FIG. 17 is a schematic diagram illustrating a side cross-section view ofanother example implantable medical device with electrodes located onmultiple housing surfaces, in which the housing includes a bellows thatallows the housing to conform to an implant site. As shown in FIG. 17,IMD 294 includes first housing 296A, second housing 296B, electrodes 302located on two surfaces 298A and 298B, and bellows-like joint 300. IMD294 is substantially similar to IMD 278 of FIG. 16. However,bellows-like joint 300, i.e., bellows 300, allows first and secondhousings 296 to change position to allow an IMD 294 to bend according totissue at the implant site of the patient.

FIG. 18 is a schematic diagram illustrating a side view of an exampleimplantable medical device with electrodes located along a bentcylindrical housing. FIG. 18 illustrates another IMD 304A. IMD 304A maysubstantially conform to the IMDs shown in FIGS. 12-17. For example, IMD304A can be subcutaneously implanted at a stimulation site adjacent aneuralgic region of the patient. IMD 304A comprises a housing 306 thathouses a control module, a battery, and a coil (all not shown).

IMD 304A also includes two or more electrodes 308 to provide stimulationto the neuralgic region of the patient. The array of electrodes may beintegrated on housing 306 of IMD 304A. Electrodes 308 may be ringelectrodes, as illustrated in FIG. 18, or may be discrete pad electrodesdistributed at various circumferential positions around IMD 304A.

Housing 306 conforms to a substantially cylindrical form factor. Housing306 may conform to a miniaturized form factor with a small diameter inorder to fit directly adjacent the painful region of the patient.Housing 306 may also comprise a degree of curvature to conform to aradius of the stimulation site.

Housing 306 may be pre-formed with a degree of curvature. As illustratedin FIG. 18, housing 306 has a joint somewhere along the length of thehousing. In some embodiments, housing 306 may permit the physician tobend the housing to a degree of curvature appropriate for a specificstimulation site. For example, housing 306 may comprise a flexiblematerial or include bellows, illustrated in FIGS. 19 and 20, that allowhousing 306 to bend.

FIGS. 19 and 20 are schematic diagrams illustrating side views of acylindrical implantable medical device that is flexible at a bellowsjoint. FIG. 19 is a schematic diagram illustrating an IMD 304B inaccordance with another embodiment of the invention. IMD 304B issubstantially similar to IMD 304A of FIG. 18. IMD 304B comprises a firsthousing portion 310 and a second housing portion 312. First and secondhousing portions 310 and 312 are connected by a bellows-like joint 314.IMD 304B includes an array of ring electrodes 316 integrated along firsthousing portion 310 and second housing portion 312. First and secondhousing portions 310 and 312 may be formed from a variety of materialssuch as titanium, stainless steel, ceramic material, silicone,polyurethane or other polymeric materials.

Each of electrodes 316 is coupled to a control module (not shown) withinIMD 304B. The physician may implant IMD 304B at the selected stimulationsite with the array of electrodes 316 within the painful region of thepatient. First and second housing portions 310 and 312 may conform to asubstantially miniaturized form factor and a small diameter to fitwithin the stimulation site.

As illustrated in FIG. 19, IMD 304B includes bellows-like joint 314 thatallows bending of IMD 304B. FIG. 20 is a schematic diagram illustratingIMD 304 in a slightly bent position to better conform to an implantationsite. For example, the physician may bend IMD 304B about bellows-likejoint 314 to a degree of curvature that conforms to a radius of thespecific stimulation site. Bellows-like joint 314 may comprise titanium,nitinol, or another biocompatible material strong enough to withstandflexing. Bellows-like joint 314 may be substantially smaller relative toIMD 304B if the material of bellows 314 is able to withstand theincreased flexing force.

FIGS. 21A and 21B are schematic diagrams illustrating a bottom view andside cross-sectional view, respectively, of another example IMD 318. IMD318 comprises a housing 320 with a top surface 322A and a bottom surface322B, each of which includes a two-dimensional array of electrodes 324.As illustrated in FIG. 21A, the two-dimensional arrays of electrodes maycover substantially the entire surface areas of housing surfaces 322Aand 322B.

Similar to the other embodiments described above, IMD 318 includes acontrol module 326, battery 328 and coil 330 within housing 320. Each ofelectrodes 324 may be coupled to control module 326. Control module 328may include stimulation generation circuitry to deliver stimulationaccording to a stimulation program via a combination of electrodes 326specified by the program. The combination of electrodes may be, forexample, a bipolar pair of electrodes on one or both of housing surfaces322A and 322B.

Control module 326 within IMD 318 can be programmed to apply stimulationvia selected combinations of electrodes 324 to achieve desired efficacy.In particular, at the time of implantation, a clinician may testdifferent programs and their associated electrode combinations, and thenprogram IMD 318 with one of more of tested programs. As mentionedpreviously, programming of IMD 318 may take place through communicationof control module 326 with programmers 240, 242 by wireless telemetryvia coil 330.

As discussed above, an IMD housing may define an angle between portionsof the housing, thereby promoting conformance to the stimulation site.In other embodiments, a housing may have a general curvature instead oflocalized angle to promote conformance to the stimulation site. Forexample, top surface 322A and bottom surface 322B of housing 320illustrated in FIG. 21B respectively are convex and concave. Thecurvature of the surfaces 322A and 322B of housing 320 may have a radiusbetween 10 centimeters (cm) and 100 cm, according to the dimensions ofthe implant site.

FIG. 22 is a schematic diagram illustrating a bottom view of anotherexample IMD 332 in accordance with an embodiment of the invention. IMD332 comprises a housing 334 that includes a rigid portion 336 and aflexible member 340, such as an overmold, that at least partiallyencapsulates rigid portion 336. IMD 332 also includes an array ofelectrodes 338 integrated on flexible member 340 at opposing ends of abottom surface of housing 334. Each of electrodes 338 may be coupled toa control module (not shown in FIG. 22) within rigid portion 336. Atleast a portion of each of electrodes 338 protrudes through flexiblemember 340 for contact with one or more tissues within a patient.

While FIG. 22 illustrates electrodes 338 on the bottom surface 82 andflexible member 340, other embodiments of IMD 332 includes electrodes338 disposed on one or more other surfaces of housing 334, such as a topsurface. Further, IMD 332 may include electrodes 338 on rigid portion336 instead of or in addition to the flexible member. FIG. 22 alsoillustrates electrodes 338 grouped into clusters at the ends of surface340, rather than extending across substantially the entire length oracross substantially the entire area of surface 340.

Rigid portion 336 of housing 334 may be formed of any of the rigidhousing materials discussed above, such as titanium or stainless steel.Rigid portion 336 may be hermetic and house a control module and battery(not shown). A coil (not shown) for IMD 332 may be located within rigidportion 336 or flexible member 340. Locating the coil within flexiblemember 340 may improve the communication and energy transfercharacteristics of coil by avoiding communication and energy transferthough rigid portion 336. The coil may, for example, substantiallyencircle rigid portion 334.

Flexible member 340 may comprise a substantially flexible polymer withtapered edges. Flexible member 340 may increase the area of top andbottom housing surfaces without significantly increasing the overallthickness of housing 334. In this way, flexible member 340 may allowmore flexibility in the placement of electrodes 338 than integrating theelectrodes into a rigid housing alone. Furthermore, flexible member 340may provide a relatively smooth transition from rigid portion 336 to thetissue surrounding IMD 332. Although IMD 332 has a larger volume than anIMD without a flexible member, e.g., IMD 332, flexible member 340 mayimprove cosmesis and prevent erosion of the epidermal region adjacentthe implantation site of IMD 332.

FIG. 23 is schematic diagram illustrating a side cross-sectional view ofanother example implantable medical device with electrodes located onmultiple housing surfaces, in which the electrodes are recessed into thehousing surfaces. Electrodes have generally been illustrated herein asbeing raised from the exterior surface of an IMD housing, such that theelectrodes and the housing surface are not flush. However, it may bebeneficial to utilize electrodes that have a small thickness to limitthe extension of the electrodes into the surrounding tissue area.Further, electrodes 338 may be recessed slightly into the IMD housing toreduce the thickness of the housing.

For example, FIG. 23 is schematic diagram illustrating a sidecross-sectional view of another example IMD 342 with recessedelectrodes. As shown in FIG. 23, IMD 342 includes housing 344 with firstand second surfaces 346A and 346B, a control module 352, coil 356,battery 354, and electrodes 348A, 348B, 348C and 348D (collectively“electrodes 348”) located on first and second surfaces 346A and 346B.IMD 342 and these components may be significantly similar to the otherIMDs and components described herein. However, electrodes 348 arerecessed within housing 344 such that an exterior surface of eachelectrode is substantially flush with one of surfaces 346A and 356B. Therecessing of electrodes 348 within housing 344 may reduce the thickness(T) of IMD 342 relative to the thickness (T) of, for example, IMD 244depicted in FIG. 14B.

In order to accommodate electrodes 348, housing 344 may includeinsulation 350A-D disposed around each of electrodes 348 to electricallyseparate each electrode from the housing. Insulation 350A-D preventselectric current from being conducted through or along the surface ofhousing 344, or otherwise effecting the operation of IMD 342. Insulation350 may be constructed of any material that does not conductelectricity, e.g., rubber, plastic, or composite materials.

FIG. 24 is a schematic diagram illustrating a bottom view of anotherexample IMD 358 in accordance with an embodiment of the invention. IMD358 comprises a housing 360, and may include electrodes (not shown) onmultiple surfaces of the housing, similar to the other IMDs describedabove. IMD 358 may also include a control module, battery and coil, theother IMDs described above. However, like the IMDs described above,housing 360 includes an attachment mechanism 362 allows a clinician orphysician to secure IMD 358 within a tissue region with suture, staples,or another securing device. In some embodiments, attachment mechanism362 may be a self-deploying or passive fixation element that protrudesfrom housing 360 to engage tissue, such as hooks, barbs, screws,expandable stent-like elements, or expandable hydrogel elements.

IMD 358 further includes a separate member 366 coupled to IMD 358 via alead 368. Member 366 may support an array of electrodes 364 on one ormore of its surfaces. In this manner, IMD 358 may be capable ofproviding PNFS or other types of electrical stimulation to two or moretissue areas that cannot simultaneously be directly contacted by housing360. Further, separate member 366 may be able to be tunneled to a tissuearea that is not reachable through direct implantation of IMD 358 or toosmall to accommodate the IMD.

FIG. 25 is a flow diagram illustrating an example method ofmanufacturing an implantable medical device with electrodes located onmultiple housing surfaces. According to the example method, first andsecond shield halves, e.g., shallow drawn titanium shield halves, areformed (370). The shield halves respectively include a top or bottomsurface for the IMD housing, and may be formed to be concave or convex,or to have an angle, as described above.

First and second sets of electrodes are located on the respectivesurfaces provided by the shield halves (372). The electrodes may bewelded or otherwise attached to the shield halves, or formed thereon byany process, e.g., a deposition process. Locating electrodes on theshield halves may include forming feedthroughs and then adding themthrough the shield halves for each of the electrodes, forming recess forthe each of the electrodes in the shield halves, and placing insulativematerial on the shield halves for each of the electrodes, e.g., withinthe recesses.

A battery, control module and coil for the IMD may be placed between theshield halves (374). The electrodes, and more particularly thefeedthrough conductors coupled to the electrodes, may be coupled to astimulation generator, which may be provided by the control module(376). Coupling of the feedthrough conductors may be accomplished bywelding or bonding. In some embodiments, a flex-tape circuit may be usedto couple the feedthrough conductors to the control module. Insulationmay be placed between the shield halves, which may then be hermeticallysealed to form the housing for the IMD, e.g., by welding or brazing(378).

FIG. 26 is a block diagram illustrating an example control module 380included in an IMD, which may correspond to control module 266 of IMD260 depicted in FIGS. 15A and 15B, or any of the other control modulesdiscussed above. Control module 380 comprises an IC 382, stimulationcapacitors and inductors 400, filter and telemetry components 404, and acrystal oscillator 406 positioned on a substrate board. The substrateboard may comprise a minimal number of layers, e.g. four layers or less,and comprise a thickness equal to or less than approximately 0.4 mm(0.014 inches). Control module 380 is also coupled to a rechargeablebattery 396, stimulation conductors 398 that connect to one or morestimulation electrodes of the IMD, and a recharge and telemetry coil402.

IC 382 may be formed as an ASIC designed to minimize the number ofcomponents within the IMD. IC 382 may be designed using the 0.8 micronprocess in an effort to reduce the overall size and profile of the IMD.IC 382 may operate substantially similar to IC 268 of control module 266(FIG. 15A). IC 382 includes a processor 384, a power manager 386, arecharge module 388, a telemetry module 390, a stimulation generator394, and a clock 392.

Power manager 386 couples to rechargeable battery 396 to provide powerto processor 384, recharge module 388, telemetry module 390, and pulsegenerator 394. Recharge module 388 couples to recharge and telemetrycoil 402 and receives power via the coil to recharge battery 396.Telemetry module 390 also couples to recharge and telemetry coil 402 andreceives stimulation programs and other instructions from a programmeroperated by the patient or physician via coil 402. Filter components404, power manager 386, and telemetry components 404 couple to telemetrymodule 390 to support reliable wireless communication. Filter andtelemetry components 404 may be selected from Table 4 below.

TABLE 4 Component Characteristics BPLUS Filter  1 uF VREG Filter 0.1 uFVDD Filter 0.1 uF Battery Bypass 0.1 uF Shottky Diode —  Telemetry TankCap 1500 pF 

Examples of filter, power management and telemetry components include atelemetry tank capacitor, voltage regulation filters, power supplyfilters, and battery bypass capacitors. Telemetry module 390 providesstimulation programs and other information received from programmers240, 242 to processor 384, which stores the programs in a memory (notshown). As discussed above with reference to FIGS. 14A and 14B, thememory may also store program instructions that, when executed byprocessor 384, cause processor 384 to provide the functionalitygenerally ascribed to processors, control modules and IMDs herein.

Crystal oscillator 406 is coupled to clock 392, which clocks processor384 to run the stimulation programs. Processor 384 directs stimulationgenerator 394 to provide stimulation to the electrodes of the IMD viastimulation conductors 398. Processor 384 directs stimulation generator394 according to the stimulation programs received from telemetry module390 and/or stored in memory, and the clock cycle received from clock392. In some embodiments, the memory may stored a plurality of programs,and processor 384 may select one or more programs from the pluralitybased on a schedule stored in memory or a signal received from aprogrammer 240, 242 via coil 402 and telemetry module 390.

As discussed above, each program may specify stimulation via acombination of electrodes that includes electrodes on a single surfaceof an IMD housing, or multiple surfaces of the IMD housing. Accordingly,respective programs may be tailored for stimulation of respectivetissues or tissue layers via electrodes in respective locations or onrespective surfaces, or a program may simultaneously stimulate multipletissues and tissue layers. In some embodiments, processor 384 maycontrol stimulation generator 394 to deliver stimulation according to agroup of programs, each program including a respective electrodeconfiguration involving one or more housing surfaces. Stimulationgenerator 394 may alternate delivery of stimulation according to therespective programs of the program group, e.g., may deliver each pulseaccording to a different one of the program, such that the patientcannot perceive transitions between the different programs. The memoryof control module 380, which may be on or off IC 382, may store programgroups received from programmers 240, 242, and processor 384 may selecta program group, in the manner described above.

Stimulation generator 394 may be a voltage or current pulse generator,and may be coupled to stimulation capacitors and inductors 400, whichinclude capacitors to store energy for stimulation pulses. Stimulationgenerator 394 may control a switching matrix (not shown) to couplestimulation capacitors and inductors 400 to selected electrodes viatheir corresponding stimulation conductors 398, as directed by astimulation program. Stimulation capacitors and inductors 400 maycontain components provided from Table 5.

TABLE 5 Component Characteristics Stimulation Cap  10 uF/20 V SeriesStimulation Cap 10 uF/6 V Bypass Cap 47 uF/6 V Inductor 560 uH

In some embodiments, control module 380 may include more or lesscomponents as needed by the IMD containing the control module. Forexample, multiple memories may be utilized in control module 380. Onememory may be used to store operational protocols, one memory may beused to save any error data, and another memory may store stimulationprograms for treating the patient. Control module 380 may be configuredto conserve energy whenever possible.

Various embodiments of the invention have been described. However, oneof ordinary skill in the art will appreciate that various modificationsmay be made to the described embodiments without departing from thescope of the invention. These and other embodiments are within the scopeof the following claims.

The invention claimed is:
 1. An implantable medical device systemcomprising: at least one implantable medical device, wherein the atleast one implantable medical device comprises a single implantablemedical device configured to deliver a first electrical stimulationtherapy to a patient via a first implantable element and deliver asecond electrical stimulation therapy to the patient via a secondimplantable element in combination with delivery of the first electricalstimulation therapy or more than one implantable medical devicesconfigured to collectively deliver the first electrical stimulationtherapy to the patient via the first implantable element and deliver thesecond electrical stimulation therapy to the patient via the secondimplantable element in combination with delivery of the first electricalstimulation therapy; and a processor configured to control the at leastone implantable medical device to deliver, via the first implantableelement, the first electrical stimulation therapy to the patientaccording to a duty cycle throughout a period of time such that thefirst electrical stimulation therapy delivery is cycled on and off morethan once during the period of time, and control the at least oneimplantable medical device to deliver the second electrical stimulationtherapy continuously and according to a selected frequency throughoutthe period of time, via the second implantable element, such that thefirst electrical stimulation therapy and the second electricalstimulation therapy are both delivered during a first portion of theperiod of time when the first electrical stimulation therapy is cycledon and the second electrical stimulation therapy is delivered but thefirst electrical stimulation therapy is not delivered during a secondportion of the period of time when the first electrical stimulationtherapy is cycled off, wherein one of the first electrical stimulationtherapy and the second electrical stimulation therapy comprisesperipheral nerve field stimulation therapy, and another of the firstelectrical stimulation therapy and the second electrical stimulationtherapy comprises an electrical stimulation therapy configured to treatpain to the patient in combination with the peripheral nerve fieldstimulation.
 2. The system of claim 1, wherein the processor isconfigured to control the delivery of the second electrical stimulationtherapy to the patient based upon receipt of a request from a user. 3.The system of claim 1, wherein the first implantable element isconfigured to deliver the first electrical stimulation therapy to afirst anatomical region and the second implantable element is configuredto deliver the second electrical stimulation therapy to a secondanatomical region.
 4. The system of claim 3, wherein the firstanatomical region comprises one of a spinal cord or a limb of thepatient, and wherein the second anatomical region comprises another ofthe spinal cord or the limb of the patient.
 5. The system of claim 1,wherein the processor is configured to control the at least oneimplantable medical device to deliver the first electrical stimulationtherapy to be time-interleaved with the second electrical stimulationtherapy.
 6. The system of claim 1, wherein an amplitude of electricalstimulation pulses of the first electrical stimulation therapy isdifferent from an amplitude of electrical stimulation pulses of thesecond electrical stimulation therapy.
 7. The system of claim 1, whereina frequency of electrical stimulation pulses of the first electricalstimulation therapy is different from a frequency of electricalstimulation pulses of the second electrical stimulation therapy.
 8. Thesystem of claim 1, further comprising a medical device programmerconfigured to communicate wirelessly with the at least one implantablemedical device to program the at least one implantable medical device.9. The system of claim 1, further comprising the first implantableelement and the second implantable element.
 10. The system of claim 1,wherein the more than one implantable medical devices includes a firstimplantable medical device configured to deliver the first electricalstimulation therapy to the patient via the first implantable element butnot the second electrical stimulation therapy via the second implantableelement, and a second implantable medical device configured to deliverthe second electrical stimulation therapy to the patient via the secondimplantable element but not the first electrical stimulation therapy viathe first implantable element.
 11. The system of claim 1, wherein the atleast one implantable medical device comprises the single implantablemedical device configured to deliver the first electrical stimulationtherapy to the patient via the first implantable element and deliver thesecond electrical stimulation therapy to the patient via the secondimplantable element in combination with delivery of the first electricalstimulation therapy.
 12. The system of claim 1, wherein the firstelectrical stimulation therapy comprises a first plurality of electricalstimulation pulses and the second electrical stimulation therapycomprises a second plurality of electrical stimulation pulses, andwherein the processor is configured to control the at least oneimplantable medical device to deliver, via the first implantableelement, the first plurality of electrical stimulation pulses during thefirst portion of time when the first therapy is cycled on, and controlthe at least one implantable medical device to deliver, via the secondimplantable element, a first set of electrical stimulation pulses of thesecond plurality of electrical stimulation pulses during the firstportion of time and according to the selected frequency when the firstplurality of electrical stimulation pulses are delivered and a secondset of electrical stimulation pulses of the second plurality ofelectrical stimulation pulses during the second portion of time andaccording to the selected frequency when the first plurality ofelectrical stimulation pulses are not delivered.
 13. The system of claim10, wherein there is a time delay between respective pulses of the firstplurality of electrical stimulation pulses and a time delay betweenrespective pulses of the second plurality of electrical stimulationpulses.
 14. The system of claim 1, wherein the second electricalstimulation therapy comprises a plurality of electrical stimulationpulses delivered at a selected pulse rate throughout the period of time.15. The system of claim 14, wherein the plurality of electricalstimulation pulses are delivered at a constant pulse rate throughout theperiod of time.
 16. The system of claim 1, wherein the second electricalstimulation therapy comprises an electrical stimulation signal deliveredat a constant signal frequency throughout the period of time.
 17. Thesystem of claim 1, wherein the first implantable element comprises afirst implantable electrical lead and the second implantable elementcomprises a second implantable electrical lead.